Indoors, is usually a lot more forgiving in focal length ranges. Most of the time I can get away with using my Tamron 25-70 2.8, and my 85mm 1.8. If allowed, I can use my 70-200 F4 with my flash (my Quantum) for the ceremony, but that's rare. Most churches have a policy against using flash photography once the ceremony starts.
That's the reason why I usually scope the location the day before, so I can get an idea of what I might need for rentals or whatever else. If it turns out I need a 70-200 2.8 IS, I'll rent that. Right now, the a lot of the photography (mainly outdoor weddings) I do simply wouldn't warrant me purchasing the 70-200 2.8 IS - yet - so I rent.
Really, I'd recommend getting a nice midrange zoom like a Tamron or Sigma 25-70 2.8, if the Canon L version isn't in your price range. They're excellent glass for the money, and you'll find people are quite pleased with them on this forum. I'm about to plunk down some cash on the Canon 24-70 2.8L soon, as I feel I use that range a LOT for my weddings.
And remember, outdoors you'll most likely be using flash for fill light - I've never really shot a wedding outdoors without some form of flash (unless I use window lights or diffusers/reflectors) - the 580 EXII or the Sigma 500 DG Super are fine choices.
Oh yeah, I almost forgot - you'll want a second body for a backup. Things do go wrong, and having a second body can save you. Plus, you can stick one telephoto lens (70-200) on one body, then the midrange zoom (25-70) on the other body to cover that range easily.
Good luck!