IMO, I'd just ask the CMs. We've had people from our party participate twice, and both times it seemed to happen because we just missed getting into a show and were the first in line for the next show.
I don't think they're really looking for people that fit certain criteria. If they are already letting people into the theater for one performance, ask if you would be able to participate in the next one if you wait. I can't see any reason why they would decline.