I'll 2nd A Class Act. I saw it done in a 100 seat theatre with virtually no set, props, or costumes, and it was brilliant because the actors could pull off playing the multiple roles as needed.
If you've got enough older actors, 70, Girls, 70 could be done fairly simply as well.
I haven't seen a production, so I don't know the requirements, but I think A Man of No Importance is one of the best scores of the last decade. I would certainly give it a look.
Zack
Pass it on - Take a kid to a show.