Walkie talkies definitely help...

but another piece of advice for not losing lots of kids in the store -- is have them wear matching, bright, solid colored t-shirts!

Seriously, it's so much easier. IMMENSELY easier, particularly when they're all little and likely to wander away.

I just get 20 t-shirts in one color, and keep them in a stack in the laundry room. No worries about whose shirt is whose.