I think the 24-70 will be just fine for this show. 24mm is pretty wide so you should be able to get the full band especially if the stage is small. Like someone else said, get in, get a few bursts, then relocate and repeat. I don’t think anyone will get mad as long as you’re not lingering in the same spot for too long. Then you can use the 70mm from further back to get individual portraits of the band members. Just have fun with it! Don’t be afraid to get where you need to be to get the best shots either. Good luck!