Seriously, it is a play, that happens to be put on by a church, I am sure they did not preach. If it was not distorted (i.e. Linus preaches about Allah), I would have no problem with it being held in a mosque. Of course the content could be presented differently, but I would expect the play notice to point it out.
You also might have to understand that since many schools have NO budget for things like plays now days, that in some cases this might be all your going to get. And typically, Christian/Catholic churches do things like make plays and invite schools to them (in some cases even busing them in if the school can't) because that is who we are.