You have the mid-range nicely covered with the 17-40, 35 and 50, but you don't have a good telephoto for weddings. I recommend replacing your 70-300 with either the 70-200 f/4 IS (my preference) or the 70-200 f/2.8 IS (bigger and costlier, but better for low light).I agree with this. The 70-200 will cover your tele needs and be good for 90% of its uses...and a tele prime would be good for closer up portraits.
I would also recommend the inexpensive but extremely good 85 f/1.8, in addition to a 70-200. That would cover the telephoto range very well.
The prime route would be to get the 100mm macro (L or non-L), the 135L, and maybe the 85mm f/1.8. That set-up could work nicely if you've scouted your locations well in advance, and you know that you'll need certain focal lengths. You'd have them all covered up through 135, which is more than enough.
But, since you are starting out, the 70-200 is gonna cause a lot less panic than switching lenses a lot