My son’s first movie was “La La Land,” which he watched strapped to my chest during a baby-friendly matinee in Brooklyn. He was 7 months old then, hungry and appropriately fussy, which means that I spent most of the movie standing at the back of the theater — nursing, jiggling, shushing — and that neither of us has seen “La La Land” all the way through. But you can’t say I didn’t start him early.For me, moviegoing is a pleasure learned in the 1980s from my own mother. She..