C.C.
We just went on vacation and used a product called "Safety Tat" http://store.safetytat.com/store/. I like the dog tag idea too... this is just how we happened to do it. You take the tattoo (which is really just a super sticky sticker) and it says "If lost call:" and you write your number on it. The pen and the sticker is water and sunscreen proof and it stays on for days. I took it off after two days because both my daughter's skin started getting a little red and irritated... They worked great. We were at Sea World and I saw this little girl talking to a police man and told him "I know my mom is wearing blue". The tats really could have helped them find her parents quickly. Good luck!