I've done my daughter's recitals for some years now... let me just say I'll personally eat my 70-200 2.8 with a knife and fork if you can pull off 1/500th of a second at anything under ISO 12,800. Lighting in these kinds of things tends to be HORRIBLE.
This means you want the fastest lens you can use at the closest range you can get. Keep in mind, however, you also want a decent perspective. Most stages will tend to be elevated over at least 1/3-1/2 of the seats... not ideal. This generally means you're going to want to be on whatever walkway is behind a large section of the seats that puts you at a decent level with the stage. This ALSO means that you're going to need longer focal lengths... which ALSO means you're going to NEED faster shutter times... which also means you're going to NEED higher ISO... which means more noise... etc. See where this is going?
What I do is generally ...
1. Shoot RAW. Intentionally over-expose your shots by about 1-2 stops and back it down in post-processing (good way to deal with high ISO noise, but does create some other challenges... like having to shoot longer shutter times)
2. Shoot manual. Get the lighting for each individual number in the first couple seconds. Usually it's just a stop or two off each time, so pretty easy to adjust. Chimp a bit and check your exposure and histogram.
3. Brace your arms against your knees or a railing or something to steady yourself... use VR if you have it. Set your shutter so you can get the motion frozen as much as possible.
4. Make sure you're not in anyone's way! Remember lots of folks are there watching their kids, so try to get a good centralish spot where you're not in people's line of site. I usually will find a spot off to the side on a set of stairs that gets me at about eye level when sitting and park my butt there for a bit. Works pretty well.
Here's an example... (mind you, I'm making no claims to composition here, just showing you what you can do if you get all the variables lined up right)
And at 100% crop (that's my daughter there)...
hmmm... something wrong with my colorspace or something... that looks way more red than it should. Odd.
These are ISO 1600, 135mm, 1/160th of a second, F2.8.
Anyway, that gives you an idea.