I don't know how old your son is, but here is my experience. I was very worried about my 3 yo son getting lost at WDW, but we didn't lose him once. He has a tendency to run off, and we have momentarily lost him in stores and parks before. I think what helped at WDW is we had a stroller. While he often climbs out of his stroller at home, he was content to look around while we were in the parks. We also stopped at all the park play areas, or just where there was room for him to run around in a convined area. Epcot's World Showcase has a lot of places that lend themselves well to this. If your son is old enough, tell him if he gets lost to tell a cast member. They have places in the parks where they take lost kids. We did buy one of those wrist leashes at Babies R Us, but we never needed to use it.
