Congrats! i stayed at All Star Music when I went with dance ten years ago and it was a blast! Before I get into the resort's offerings I just want to say when you are there make sure to take LOTS of pictures and take a moment and just step back and appreciate this awesome opportunity! Very few kids get to say they performed at Disney so appreciate every moment!
As far as the resort, make sure you have change for the arcade! It's a really fun way to wear down extra energy and its so fun! If you want you can have pizza delivered to your room and the pools are sweet! Also make sure to bring a little extra cash for the gift shop. Right now they are selling a lot of mementos that have "All Star Resorts" on them and being able to bring home a mug or ornament or something with the name of your resort is a great way to remember your stay! If they don't have any when you go you can always find some on eBay : ) Have a GREAT time! Enjoy every moment!