Hi Cleyvosier - without reiterating what amirg said I too would also use the 7D as your main body.
Your best chance for adequate exposures will be to use the 85 f/1.8 - a fine, sharp, fast lens I own and enjoy - along with ISO 1600 to start. That will give you a little bit of noise, but it will allow you to use higher shutter speeds to freeze action and bit more DOF when you need it.
Hopefully the lighting will be somewhat uniform in the church. If it is not, identify the main, different lighting zones. Since you own a light meter, that will be an advantage. Get INCIDENT meter readings in these spots which will tell you how much light is falling ON the subjects. A reflected reading will be anomalous in these circumstances since it will be reading white dresses and black tuxedos. Once you get a solid reading, set your camera on MANUAL with these. MANUAL will lock it in so it won't fluctuate. As long as you are in a uniformly illuminated area, it is to your advantage to have the metering locked in. You can always check by chimping the LCD and looking at the histogram, although the later may not be terribly useful in dark areas.