I think you can pull off some shots with what you have. I'm guessing you only have something like an 18-55 kit lens that came with the camera?
Here's how I would approach it in your shoes.. put the camera in S mode, that lets you set the shutter speed. Set the shutter speed to 1/125 (if you're unsteady you may want a little faster than this or a little slower if you have IS), this should cover you with an 18-55 with some stage movement. Start with the ISO around 800. It may or may not get the exposure, depending on how bright they have the stage. If it doesn't, keep bumping that ISO up until it does. If you get to your ISO limit and still can't get the exposure then make the lens wider (to the 18mm end) and you can slow the shutter speed down, but I wouldn't go too far.
NOW... if you can get a tripod in there (a lot of parents I know will tote one to things like this) you can bring that shutter speed way down probably to 1/15, or slower if they're not moving really fast on stage, since you'll be eliminating the camera shake. If your lens has IS and you will want to turn it off if you use a tripod.