I'm not an expert..
The 5DIII with the 24-105 plus flash (when needed) is great.
The 7D yes. However a crop body with the 70-200 may be a bit too long depending on the size of the venue.
what do others think?
A second flash might be good to have, but that is a lot of clunky stuff to carry.
I don't even try to say I'd be an expert, if I was I might not need to ask for opinions. I'm just a happy hobbyist, and instead of inventing the wheel again, I'm hoping to learn from other peoples' experiences.
But I don't see how the 70-200 would be too long on crop, especially as the 24-105 almost seamless continue from there. I don't know the size of the venue, but I'm sure the 24-320mm will cover anything. Bit wider might be nice on occasion, but 24 on FF does quite good work too.
And if I'm carrying already 2 bodies, it's not really different size-wise if I have flash on both, compared to flash on one. If the venue seems small/tight, I might drop the 70-200 and shoot mostly on 24-105, and maybe for some candids I'll change the 70-200 on 5D. I've been hoping to get double-RSS straps, but too late now. Have to deal with the standard straps.