Randy, the questions/advice Jeff offers here is spot on. I too won't try to discourage you from doing this, but there is so much more than just putting up some monitors for people to view on. How much time do you have to get ready for this event? You will need event viewing software and someone working the table how can trouble shoot any problems that come up (and they will....). You need a way to take payments. You need insurance. Are you prepared to market yourself? Lets hope you have good lighting.
If you can't secure the sale before the parents leave, you will likely never see that sale again. With this being the beginning of the cheer season, there is likely going to be another competition just around the corner and once the parents get there, they forget about the pics from the last event....
If this is a decent sized event, you will have a few thousand images at a minimum, so editing onsite is out of the question. You have to get the exposure right in the camera so that you have minimum editing for any ordered images. When Jeff says it can get expensive quick, I think thats an understatement. I am very small when it comes to this game, and I spent ~5K just to get started, and thats only the viewing station equipment!
If you are not familiar with all-star cheer, be ready because these girls can move!
There is a ton of info, but I have a tendency to ramble on, so I'll stop here...
Good Luck, Lance.