What is the lighting like and how close are you to the subject?
Most likely, the flash will not help you at an event like that unless you are very close to the subjects. Your best bet is to use a fast lens (2.8 70-200 zoom) preferably with image stabilization, then pump up your ISO (400, 800, or even 1600). You will get a lot of noise at those ISO settings, but you can remove it later in Photoshop (Photoshop Elements, Photoshop CS2, Noise Ninja, or Neatimage). A tripod is helpful if you can set one up...you might want to check if it's allowed. For better mobility, consider a monopod. You can rent all this from a photography store if you have one nearby. Have a great time!