When we traveled with our niece and nephew, we did as other posters have mentioned and had IDs made at the Department of Motor Vehicles. I kept the originals with me and put color copies of them in each of their waste packs so they would always have some ID if accidentally separated from us. As also previously mentioned, we obtained signed medical treatment authorization letters from my sister. Since we were traveling by air, we also had a signed notarized letter giving us permission to travel to WDW with the kids so no one would think we were taking the kids without permission. We never needed them, thank goodness, but felt much better by having them. I created all the letters from a software package containing legal forms for families to help insure all the legalese was correct. Have a good trip!