What most naturally follows?

How to handle holiday shopping with your kids
Explain what you expect from your children.
Before you get to the store, explain your rules to your children. You can't expect them to behave if you don't lay out what behavior you want from them.
Plus, telling them right before you go in keeps them from weaseling out of situation by saying they didn't know any better. Don't go during snack or nap time.