Great idea if you will be heading out for vacations in busy areas. Pick up a pack of 36 Tig Tagz personalized id bracelets for your kids.
Personalize them with phone numbers or medical info (this would be great for allergies). Tear-proof, sweat-proof, smudge-proof, and water-resistant to survive a busy day of fun! $15 for the pack + $1.29 shipping.