Where the parade stops is pretty random. It has to do with where the parade is in the music when they stop. It's all choreographed and we have seen the dancing happen in front of Pecos Bill, when the parade turns the corner onto Mainstreet, and at Mainstreet before it loops around (near the photoshop) So there is really no guarantee on that either, nor that your son will be chosen. Our middle child was chosen and our older child wasn't (talk about a pouty tween for the rest of the day!) Of course our middle child was already bopping to the music so that may have made the difference. Almost 6 years ago I got to waltz with Prince Charming (Cinderella's)!! I can remember it clearly because I was so dizzy and I didn't know if it was the excitement of dancing with a prince, swirling around in the dance or symptomss of early pregnancy LOL!! (I was 6 weeks pregnant) I was just standing there beaming nearly crying (like I usually do) and there he was holding his hand out to invite me to dance!
I miss TON/D parade at Epcot. The puppets were very interactive in those parades and we have lots of pictures of our kids dancing and shaking hands with the puppets!
It's all random, but they do notice kids that seem enthusiastic (into the music, clapping, already dancing) but not pushy (like jumping up and down going "me me me me")