For event photography, the first thing you need to do is upgrade your core lens. In this case, there is an excellent option in the EF-S 17-55 f/2.8 IS USM.
You should also get a backup camera body. Perhaps you can borrow one for this event. My 40D's mirror failed at a wedding reception in Cancun. Fortunately, I had my trusty 20D with me, so I could keep shooting.
i was looking at the 17-55 its a nice lens but for only 200 more i could get 24-70L but would that be wide enough on crop?