I think the best advice is to tell children to look for a CM (easily identifiable by name badges) if they become lost. The CMs are trained to take good care of them.
We lost my just turned 10 year old at BB last year, and I was frantic. We have 3 kids (DS-10, DD-6, and DS-3). We were all in the wave pool, and the 10 year old got out to sit on a chair. I decided to head back to our chairs over by Tikes Peak to get sunscreen before we headed to lunch, and left my DH watching the kids. When my DH noticed the 10 year old was gone, my DH figured he had gone with me. What had actually happened was the 10 year old had looked up and couldn't find us--he didn't have his glasses on due to the waterpark which probably didn't help. He therefore left and headed back to our chairs by Tikes Peak. I didn't know he was headed there. When he couldn't find us, he found a life guard who had him stay beside her while she radio'd for security to come to get him to take him to the 'Lost Kids' picnic table. Meanwhile, I ran back and forth between the wave pool and our chairs at Tikes Peak looking everywhere for him (and also checking in at 'lost kids') while my husband sat with our two younger kids waiting exactly where we had left our DS. I was a nervous wreck. Eventually, on one of my passes by the 'Lost Kids' table I found him sitting there.....the security guard had walked him from the LifeGuard to the table. Evidently this whole 'lost kids' thing is a very frequent occurence.....many every hour at BB. Was definitely an agonizing 30 minutes though!
Even with a set meeting place, I don't think I'd want kids to be wandering around or waitng by themselves, so I think the CM approach is a good idea.