Unless your in a dungeon, you can use your 24-105 for the ceremony. I used my 70-200 f4 IS for almost an entire wedding with the 7D. If your going to second, you should be able to use your primes at will, but I believe your 24-105 is going to be a little more useful. You don't want to miss a shot because your changing lenses during the ceremony. Don't be afraid to use ISO to keep your speed up since noise is easy to clean up. Heck, some people even add noise for artistic effects.