The moms snap away. Santa and Mrs. Claus, whose off-duty names are Lou and Loretta Knezevich, can’t hear the compliments. They’re deep into discussing good behavior and the latest in Lego.

Camera phones at the ready, a pair of moms watch as their sons flank Santa and Mrs. Claus in the restaurant of the St. Regis Hotel in Buckhead. Bryce Milbury, 8, ascends Santa’s lap. Bold, red ...