What a great opportunity for those children and how nice of you to want to make it worthwhile for them.
My daughter is in the color guard and going with her marching band this weekend. She is lucky enough that we get to go quite a bit, but many of her friends are just as you said, have never been before, and may not be able to go again for a long time. What a great experience.
We are a group of about 80 band members, with a few families doing the tag-along to watch(yay us
). We are hoping also the crowds will not be too much as the kids will be sharing park time with performances and workshops and hope they will be able to ride as many of the things they want as possible.
They will be allowed to roam the parks on their own as they are in high school, but have been read the riot act and are a bunch of very nice, respectable young adults.
Good luck to your daughter and we may be in the MK on the 25th, if we are we will look for their performance.