Gavin, I think the first question has to be.. how big, and how experienced are you expecting the cast to be? That will certainly help in identifying which of the myriad of shows might be better suited to your need. As far as "simple sets/costumes", I can't stop singing the praises (though the kids in our program *really* don't want to hear me sing) about "Dear Edwina JR.". It's also easy on the blocking/choreography, due to the segmented nature of the presentation. Check it out.. there are plenty of images and youtube video's out there.