The last time we went my sister came and so did my parents. I made ID cards for the children. I took photos of the children (at the time ds7 and dd10, three neices 12, 5, and 1) and imported the picture into an excel document. On it I listed their names, nicknames, home information, medications taken daily, and medication allergies. In addition, I also listed our resort information, our cell phone numbers and then I listed 'also traveling with' and listed my parents and my sister's names and cell phone numbers. Each ID card was lamenated.
They carried a copy of this in their waist packs. They had strict instructions that they were only to take them out if they were separated from us, and only for a cast member. I kept a duplicate of my children, my sister kept a duplicate of my neices.
Thankfully we never had to use them. But if we had, all the information was there.