another rthing we have noticed is that kids with ADHD can wait a lot better for attractions they want to see than those they don't care about.
We're pretty used to DD (who has ADD, among other things).
A few years ago we took our nephew, who has ADHD. He was very good waiting for things he wanted to go on, like Space Mountain. He had a lot of difficulty (to the point of sitting on the ground and refusing to move) when we went on some things like Country Bears that he had absolutely no interest in. Once he was in, he was fine and enjoyed it, but since he didn't really know what it was, he wasn't interested.
One book that is really good for kids is called Walt Disney World for Kids, by Kids. It's nice because it is written from a kids point of view and covers things like - how scary is it.
That can describe just about any kid, don't over focus on the ADHD thing!