to the OP: honestly you are are going to be fine with your current set up. If anything do as others have suggested and buy/rent a FF body.
Obviously if you are doing this for friends you want to make sure their day is special, but since you aren't being paid don't go over board with a bunch of stuff you have to cart around with you all day. After all I assume you want to enjoy the day celebrating your friends as much as you want to also capture it. Set expecations low, then they will be pleasantly surprised when you deliver the goods!
If it was me, I'd bring the 7D, 24-70, a flash, and be done with it.
You will get one or two stops better high iso noise performance on a 5DII than a 7D, which makes up for slower lenses. Keep in mind that the wider your aperture, the greater your risk of misfocusing. Especially when you are shooting your first few weddings, it is possibly better to be conservative in what you shoot.
My wife's experience has been that there is little time for changing lenses. Especially at the reception, you risk missing shots. Her first couple of weddings, she shot almost exclusively with the 24-105 f/4L (second shooting). She now takes along the 70-200mm f/2.8 IS II, 50mm f/1.4 and 15mm f/2.8 fisheye (that is really an optional lens, but it doesn't weigh much).
Her biggest complaint at the moment is the AF system on the 5DII, but that will get sorted when she gets a 5DIII.
The 5DII is a much more forgiving camera than the 7D, despite the fact that the 7D has better AF. If you are under pressure, that counts for a lot. Using good bounce flash technique, you can get away with pretty poor light and a f/4 lens with the 5DII.