I would recomment that if you do not want to use flash, go for the prime lens.
Otherwise, for indoor event, having a external flash is almost a must. First to capture motion, bumping up the ISO may not be enuf. Second, for proper fill in flash for people shots. Without flash, the people shots may look dull and bland in a low light environment, fill-in of shadows.
Third, with an external flash, it should help in the focusing in low light condition.
When shooting a wedding, you would be worrying about capturing important moments, shutter speed is more important, IS is secondary.
Well, if if it is outdoors mainly or area with lots of good lighting, i believe the 24-105 would be enuf. For the other lens, 10-22 gives too much distortion and not recommended for standard wedding and people shots. The 70-200 would be nice outdoors for the reach and portraiture shoots. 100-400mm, not as suitable as 70-200 bcos its large heavy, not a fast lens.
But i worry if 24mm is wide enuf on your 30D, i often have to go 17-20mm for the table shots. If just taking candid shots, 24-105 no prob.
I would strongly recommend a flash still, even in daylight, to do some degree of fill-ins
Since you are the backup fotog, just enjoy shooting the wedding, with some preparations. Oh, just one caution from experience, try not to get in the way of the main photog, give him space as he responsible for getting the "money" shots. While you can catch other activities happeneing ard the couple, eg the guests, friends etc
hope it helps