For most little kids, a trip to the supermarket is an annoying chore, made tolerable only by the opportunity to request sugary snacks as a reward. But when Charlotte McQueen accompanies her mother, Erin, to the store, it’s a journey marked by imagination and delight. “Mom, can we get that?” she asks, pointing to a can of pureed pumpkin. “Oh, and we’ll need marshmallows and we can make chocolate frosting. It will be a great cake!” …