My husband is in law enforcement, and I have heard and he has lived enough horror stories that I am surprised my husband hasn't ducted taped my daughter to his body, much less let her out of the house. Obviously the best thing is to keep your children near, and while it is very often a careless, negligent parent whose child is lost or injured, the truth of the matter is it could happen to anyone. We watch our daughter like hawks, but there has been an instance at the zoo where her excitement got the best of her, and her little hand slipped out of mine, and off she went running. If that has never happened to you as a parent, you deserve the parent of the century award, and I'd like to shake your hand.
I think the tattoos are an amazing idea, and we plan on using them when we go. I think putting it in a less conspicuous place like the inner wrist or ankle is best so it's still obvious, but not everyone can walk right up top your kids and see their name in the outside of their arms. I think telling them the name of your resort helps as well. The more info. they know, the better!