I wouldn't go with something much longer than 50mm on a crop body, especially if your close which more often than not is the case. I did the
MVMCP both with a flash (point & shoot and older film SLR) and without a flash (dSLR with a 50mm f/1.8 lens). I MUCH preferred the no flash images.
We got a spot in Frontierland on the steps of the Diamond Horseshoe. There were some extra lights there that helped a lot. I'll post some shots later when I get to my computer.