If you are the main/only shooter, I doubt you'll have a chance to do video as well as shoot, because all the bits that want videoing are the bits that want photographing, unless you plan to put a camera on a tripod and leave it.
Two bodies is very useful as said, you can have 2 lenses on the go at once.
I would have the 24-70 on the 5D3 and the 70-200 on the crop body. You won't want the 70-200 all day, you can put that down at various points and the range of the 24-70 (and f2.8 on full frame) will be enough to shoot a lot of the day.
If you're not being paid, I'd try to borrow a crop sensor body off someone rather than payout for a body that for 95% of the time you're not going to use. If you can do that, but still want to spend some money, I'd get a good 50mm prime, the f1.2 L is what I'd get, (I loved the one I borrowed) or the f1.4 is good for £250.
As for lens choice during the day, I'd say that it can depend on the venue.
If it's in a pretty church or country house, you can go for wider lenses to capture the pretty location, but if it's a simple registry office, function room or in a marquee, you'll want to go close with a longer lens to focus on the couple and eliminate the less pretty venue.
Obviously you don't have to stick to just these, and having other decent lenses on hand gives you options.
I photographed an Arabic wedding in June and they had a traditional procession with drummers and chanting and stuff that took about 20mins before the ceremony started. For that I had 2 cameras on the go, one with the 24-70 f2.8 and one with a 70-210 f4. This covered all bases. Then once they'd moved into the marquee with horrid lighting, I mostly used the 24-70.
But it's all down to how you want to capture it.