My little one (3.5) was the 3rd kid picked on our first try last week. He was wearing a yoda stitch shirt (from the disigners on the boards) and the Jedi master was immediately drawn to him. He even got to stand on the blue circle immediately to the right of the jedi master and got lots and lots of attention throughout the entire show.
Funnily enough, the little boy next to us, who had to be around 7ish, ended up "choosing" himself to be in the show and the helpers didn't catch that he hadn't been "chosen" and thus he was allowed to participate. At first his mom was freaking out because she knew that he hadn't actually been picked. But, once he was successfully in, she couldn't help but be proud as he has apparently chickened out on participating several times in the past.