In my experience of shooting weddings, you need something longer than 50mm for the ceremony and reception, unless you don't mind getting in the way! Even if you don't mind, I guarantee the registrar/priest/video guy certainly will!
200mm is a useful range to discretely position yourself off to one side of the service and not be too obtrusive, although shutter noise always sounds like a gunshot in a church anyway!
Sounds like a 70-200 f2.8 is what you're looking for, it's what I use at any rate?
If so, then Tamron and Sigma both make decent ones, with the Sigma in particular being pretty quiet focussing wise due to the HSM. The Tamron is a good lens also, but has a noisier focussing motor. You could always focus manually though. Bear in mind that not all examples of those lenses will be as sharp as you'd like wide open, which is where you'd be wanting to use them. Cranking up the ISO and sorting the noise in post processing is an option, and then you could get away with f4 where both those lenses are very sharp.
I'm not a user of Canon equipment so I'm not familiar with anything they may have that's suitable, so I'll let others comment on that.