We plan to have our kids both wear the same clothes on the same day -- that way, if one gets lost, we can show them what the other child is wearing. Also, carry current photos of your child at all times. The family photo idea is great. Each child is getting a fanny pack to carry, and I plan to laminate the photos and put our info on the back.
Also -- I will be putting the family name on the inside of their shirt collars -- near the tag.
In terms of lost kid, my kids are at much greater risk for running off through a crowd than anything else. I will explain at the beginning to look for a CM if they are lost. Cell phones will be key to this process, I think.
For the first 2 days, we have a 2:1 ratio of adults:kids. For the rest of the trip, it's 1:1...we'll just make sure we know which adult has whom at which time.
I have to admit, this is a pretty scary thing for me.
Laura
DS4, DS2.5