-Have you asked anyone in the 'weddings' forum?
They will be the 'experts' to ask about what lenses they use and why.
You really need to cover from 10 to 300mm but that is not always practical 
I think anything wider than 17mm on a crop body is likely to introduce severe distortion at the ends of any group shots, although I'm sure if you keep the camera level you can get away with wider.
The 24-70L is by all acounts a good lens, but I'm sure you will find it not wide enough for a lot of group shots.
You say you have (or will have?) a 70-200 so that will cover that range OK, you may have to have 2 others to cover the 10mm to 70mm range, but if I had to chose just one lens to compliment the 70-200 it would be the 17-40L although it is 'only' f/4. You mention the 17-55mm that would give you a bit more range and it's faster (and more expensive!)
You may need a 50 f/1.4 to fill the gap and this would make a great low light lens as well.
The options are quite varied I'm afraid...