Don't do it.
I know sometimes you have to, but I would just try to avoid it if at all possible.
I have a 12, 5, 4, and 2 yr. old. The 12 whines and asks to have every magazine that even references Twilight. The 5 yr old is the boss the tries to "help" me shop by grabbing everything she sees asking if I want to get it. The 4 yr just runs and cart and tries to destroy it(He is boy in case you hadn't guessed.

) and my lovely baby is impatient and has a small window for persuing the aisles. Put them all together and I am a madwoman in the store. So I leave them at home with daddy or whoever I get to watch them(for free).
Children and saving $$ just doesn't hand in hand.