I agree with putting warmups or something over the uniform, but in your OP
Num1Stunta you said to actually change out of it. I guess my problem with this is where on earth would this changing take place??? Certainly not the bathrooms - its already bad enough in there with the hair and makeup. This isn't like a normal performance group that has a limited number of people. And it's not like Dance Moms where each team is apparently given their own room to get ready in. We're talking a few hundred kids over the course of a day... Where would you have them change at a typical competition venue?
(***This is not necessarily to disagree with you. Just questioning the logistics of how you would actually make it happen)