Id go with the 24-105, and 50mm as well. My T1i was a little noisy above 1600 ISO, I hope you won;t need a real High ISO. My advice from shooting under pressure,
shoot in RAW: better noise reduction avail in post as well as other modifications
Find a good balance between analyzing each shot, and spray-and pray: Ive over-done both situations and found few keepers, but with a good balance I end up with more keepers
chances are if they picked you, they have seen some of your work, and you have more talent than them, and they will like what you shoot, so dont stress (I cant actually do this in practice)