There’s a special screening in Chestnut Hill Sunday of Jennifer Garner’s new film, “Miracles From Heaven,’’ and we’re told the actress — Ben Affleck’s soon-to-be ex wife — will be there. The screening at Showcase Superlux is a benefit for Boston Children’s Hospital, which makes some sense considering that the movie, based on Christy Beam’s memoir, is about the near-death experience of Beam’s daughter’s from a rare, believed-to-be-incurable disease and her subsequent, and quite miraculous, recovery. In addition to Garner, Beam and her family, including daughter Annabel, will be at Sunday’s event, as will Dr. Samuel Nurko of Boston Children’s Hospital, who treated Annabel. “Miracles From Heaven’’ opens March 16.