SEDONA, Ariz. — Two women in sunglasses step gingerly into a hot tub as the sunset paints the prehistoric spires of Arizona orange and red. They start talking. And listening. And talking some more.

“I don’t feel old, Myra,’’ one says.

“But Millie we are,’’ responds the other, as they soak and converse in the bubbling warmth, where buoyancy reduces stress and pressure on aching joints.

It’s Day One of a four-day journey into Northern Arizona’s mystical buttes and canyons, and I’m tagging along with two octogenarian psychotherapists from suburban New York: Millie (my mom, 88, recently and reluctantly retired) and her best friend Myra (85, who still sees 30 patients a week).

For more than 50 years, Millie and Myra have seen one another through major life events: joyful graduations, weddings and grandchildren, but also arthritis, chemotherapy, a heart attack, high blood pressure and profound loss, including Myra’s husband. They go to funerals for friends. They take fistfuls of medication. They never complain, but when pressed they might acknowledge: “Once in a while, we kvetch to each other.’’

It’s not lost on them that our trip is beginning in a paradise for hikers, Sedona’s red rock country, a place of dramatic trails that are especially appealing on this cool October morning. Mountain hikes are out of the question now, so we linger over coffee and huevos rancheros at El Portal the rustic arts-and-crafts hotel on the banks of Oak Creek. We talk about the big challenge ahead: Visiting Antelope Canyon.

Both Myra and Millie are nervous about walking in and out of the hugely popular slot canyon in a Navajo tribal park near the border with Utah, where water has carved winding paths through delicately lined rose-colored stones. We’ll be visiting the upper part, which, unlike lower Antelope, won’t require climbing stairs. But it will involve navigating narrow, enclosed spaces for about a quarter of a mile, sometimes in darkness.

Antelope is only accessible only via Navajo guide, and tours must be reserved months in advance. But this trip is not just about seeing Antelope: It’s also a nostalgia journey, to the place Myra lived and loved before her desert childhood ended suddenly. She had moved to Arizona when she was 9 and left at 13 after her mother died. Back east, Myra lived with an array of different relatives in Brooklyn and never got over missing the stoic beauty of the American Southwest.

It took 25 years before Myra could once again see the little adobe house of her childhood, even though a new owner wouldn’t let her come inside. This time, a half century later, she’s bent on sharing her love for a land she spent too many years missing with her close friend Millie.

“I don’t have a relationship with the desert; I guess that’s why I’ve never been,’’ says Millie, who grew up in a Bronx tenement and is drawn to oceans and salt water harbors framed by lush foliage.

As we set forth, Myra becomes Millie’s mentor, exclaiming over Arizona’s layers of sandstone and sediment and petrified wood, the ever-changing brown and endless ocher vastness. “The desert was my freedom,’’ Myra says. “The desert is where I got on my bicycle and rode and rode and fell in love with the landscape.’’

Along the way, they chat and I listen, while our excellent tour guide Stephen “Benny’’ Benedict, founder of a private adventure company known as Earth Tours, handles driving and details. Benny is the ultimate former Eagle Scout and national park ranger, who seems to know every inch of Red Rock country, along with everyone we meet along the way. He’s carefully planned our itinerary, from meals to hotels to backroads we never would have found on our own.

He is also trained in first aid, a comfort for family members who balked at what began to be known as the “Thelma and Louise adventure’’ to Antelope Canyon. When word got out, a strong consensus emerged that Millie and Myra should not go it alone, given their ages and various medical conditions. That’s why I’m along, even though Millie and Myra protested at first, and in truth, didn’t really need me.

Sure, they have aches and pains, but they are not to be discussed. Nor are bum knees, bunions, neuropathy and other ailments. “The only way to live with all this is to ignore it,’’ Myra says. “If we accept the changes in our bodies as we age, we are going to have a better life.’’

In younger and healthier years, Myra camped and hiked in all 50 states, and took nine vigorous bike trips with her close friend Dot through Thailand, Tuscany, New Mexico, and the Rockies, among others — an impressive peripatetic resume. “I’m not against pushing myself, but respectfully,’’ she says.

“At our age, you have to ask yourself, to what end?’’ Millie responds, an admission she makes with difficulty. For decades, Millie began most mornings with a long walk, often in time for sunrise. Now, more than 10 years after double knee replacements, walking hurts. I can see grimaces she tries to hide with a smile.

Still, I understand why the two bristled at being told they are too old to travel without help. Who wants to be handled like a fragile piece of china? “I do not like it if anyone takes my arm,’’ Myra says. “And I just hate that way of being talked down to, that condescending ‘How are you, dear?’ ’’

Millie responds instantly: “We can’t stand being treated like little old ladies.’’

Our guide Benny understands: he’s neither too solicitous nor too hands-off. Instinctively he knows when the two might want a hand stepping down from his SUV, or a rest, or when a margarita is in order instead. Benny also factors in hot tub time, where visitors flock to the pair and reveal all kinds of personal details, even though Millie and Myra have a pact: Never tell anyone you are a therapist on vacation.

With Benny at the wheel, there are few logistics to worry about: no maps or navigation devices, no getting lost and fighting over directions or looking for hotels or restaurants. Benny has insider knowledge of Arizona’s back roads and hidden vistas, and we are free to watch, listen and learn.

Previous desert forays with my husband and boys (both now in college) always involved long hikes followed by setting up tents and gathering firewood. Now, I am simply listening, laughing, and soaking up wisdom and great company, starting with our first (and my favorite) meal at Mariposa Latin Inspired Grille. The setting will pop into my head forever when I dream of flaming cliffs and smoky craft cocktails. We watch the sun go down, followed by an enormous moon rising over the canyons.

Benny is the one who makes sure we are up early enough to observe the bird life in Oak Creek Canyon, the Ponderosa pine forests on the Colorado Plateau, and the landmarks along historic Route 66. He’s also planned a stop at the Winter Sun apothecary, a family-owned shop stocked with Native American art, traditional Hopi Katsina carvings and a stunning array of attractively bottled and packaged organic and wild crafted herbs.

Since there’s an ointment or organic potion for every ailment, we spend a lot of time here. Myra and Millie each fill a shopping bag with native herbs and curatives. I’m content with deep penetrating arnica liniment, promising soothing relief from aches and pains that will only get worse.

On the road, we stare at endless ribbons of highway and desert mountains outside our windows. I hear about Myra’s childhood, how she hated moving back East and becoming the last girl picked for basketball. I learn how she was rescued on the court by her friend Dot, who taught her to pass the ball and became a lifelong friend and travel companion.

I hear about how Millie and Myra each married at ages that would now be considered absurdly young (19 and 20), and how they later carved out careers, joined consciousness-raising groups and marched for civil rights. Millie juggled graduate school while raising children, while Myra crash-learned Spanish so she could enroll in Puerto Rico, where she was living at the time.

I hear how Millie and Myra first met and instantly clicked while working at a mental health clinic, and later started private practices where they’ve treated over a thousand patients of all ages and issues.

By the time we pull into the small town of Page, sunset is underway over the southwestern edge of Lake Powell, the enormous man-made reservoir straddling the border of Utah and Arizona on the Colorado River. This is the moment Myra has been waiting for: she wants Millie to see that the desert isn’t entirely dry.

“Oh, Myra, is that the water we see?’’ Millie asks. “How can that be?’’

The juxtaposition of blue water, red cliffs and boats seems almost mirage-like. And we’ll soon be surrounded by water, staying at the sprawling Lake Powell Resort at Wahweap Marina, three miles from Glenn Canyon dam. There are busloads of tourists, but also several pools and hot tubs that look over stunning rock formations and impossibly turquoise water.

Benny checks on reservations for our all-important next day journey to Antelope Canyon, and we later toast our upcoming adventure over margaritas and Mexican food. The night air is crisp and inviting, so I decide to drag a few blankets out and sleep on the outdoor balcony, the better to see a desert sunrise.

By dawn, we’re getting ready to meet our Navajo guide outside of Upper Antelope Canyon, which unlike the lower canyon, has no stairs. Still, Myra and Millie are getting nervous. Normally, Myra takes a steroid with breakfast, but we’re up too early and she’s concerned her legs won’t hold out. Millie worries about stomach and foot problems; she regrets last night’s margarita and her choice of sandals.

Both are uncharacteristically silent while Benny deals with a few mix-ups with meeting spots and guides: Myra is worried she won’t see Antelope Canyon after all. Finally, we’re loaded into the back of trucks shortly after 8 a.m., driving 3½ miles down a sandy road to the entrance. Myra is in awe: she steps gingerly into the canyon but never stops smiling.

Millie allows me to help her through darkened portions of the canyon where you cannot see the sky. A guide who knows the best shots offers to take a few pictures on my phone. Others around us snap photographs frantically, while we mostly stare in wonder and listen to haunting native American flute music in the background.

“I am in love,’’ Myra says. The foot tour lasts less than 90 minutes, and we come out relieved and ready for a celebratory breakfast at Ranch House Grille, accurately described as the place “where the locals go to eat,’’ with specialties like Frybread.

Later that day, we have another chance to see Antelope Canyon from a different and far less intimidating perspective: on a boat cruise along Lake Powell’s towering canyon walls and buttes. Myra, who waited 25 years to see Antelope Canyon, is in tears. “I can’t believe I finally got to see Antelope Canyon today, and now I’m seeing it again,’’ she says. Millie gives her a hug.

By nightfall, we’re at the historic Cameron Trading Post, where the Hopi and Navajo for years gathered to barter wool, blankets and livestock for dry goods. It’s also a chance to buy turquoise, silver and other native crafts at great prices. We spend the night here, stepping carefully through levels of landscaped gardens.

In the morning, we drive to the all-white Coal Mine Canyon overlook, one of the most beautiful (and least known) canyons in the world. The rest of the trip back to Sedona takes us through the candy-colored striped mountains known as Painted Desert, where Benny points out 200-million-year-old pieces of petrified wood. We also drive along stunning Schnebly Hill Road, with its steep clips, wild twists and hairpin turns along unpaved roads that drop more than 2,000 feet from a wooded mesa. This is not a drive for the faint of heart.

By the time we pull into Enchantment Resort, there’s time for more water exercises and hot-tub soaking at the foot of red rock-boxed Boynton Canyon, part of the wildly diverse Cocino National Forest.

This hotel and spa is far more luxurious than any I’ve ever stayed in, and perhaps for Millie and Myra, too. But along with cherished memories, that’s part of the beauty of aging. When I inquire if it’s too expensive, they answer simultaneously, with laughter, “What are we saving up for?’’

On our last morning, I sneak out for an early morning desert run before the hardest part: putting on shoes and packing. We say farewells without getting sentimental. Don’t dare call this a bucket list trip; Millie and Myra both find that phrase too annoying.

Besides, there are still a few more canyons they haven’t yet seen. “I really can do another one,’’ Myra says. “And I need reassurance that I’m coming back.’’

Meantime, there’s a final concession to aging: wheelchairs at the airport.

Follow Liz Willen on Twitter @L_Willen