We went last year with our ds (then 9). The show is right next to the Star Tours ride. They have a training session every hour or so. You gather round, the trainer asks if anyone wants to be a jedi, the kids jump up and down and the trainer points at children to select them. He choses many children....probably 20-25. The parents stand in the audience and wait...I didn't see any parents going up with children. The children go up on the stage (the show is outdoors) and get robes and a lightsaber and they have a training session and then each child gets to fight either Darth Vader or Darth Maul for a few seconds. Who you fight depends on what group you're in...there are 2 groups. Afterwards, each child gets a jedi training certificate and an action figure.
We had one boy in ds' group who started crying when Darth Vader approached and he was quickly hustled away. I didn't see many children under 6 on the stage.
We went to 2 shows before ds was chosen. I noticed several parents did this. When he wasn't chosed for the first show, we went and did something else and came back for the 2nd show. Then he was chosen. It was worth it. It was one of the highlights of the trip for ds.