Kind of unfortunate that there is so much negative feed back to your question... Everyone has to start somewhere.


I would say renting another camera in the rebel line would be a safe bet (read T2i or T1i). Other than that - if you get a 70-200, I would think with that on one camera and your 17-55 on the other you would be in good shape for just about every shot you would want. I did not notice you mention a tripod, you may have this covered but I find it an essential item for this kind of work.


With that said, if you really wanted to step up in terms of image quality, I dont think you get a truely noticable gain until you go to the 5D Mrk II. And I agree with some of the others here, learning a new camera at a shoot for money is very risky. It would be better to rent that for a fun/practice shoot so you are ready to use it at the next opportunity.


Good Luck!