For me the 35L is the first choice. The image quality it provides are superb, and it's actually pretty good wide open. I choose it over the 50L for 2 reasons, I don't think the 50L is an amazing lens compared to the 35L and also the 35L allows you to come closer to your subject hence avoiding people getting in between you and your subject(s).
Then I'd go with either an 85L or a 135L based on the layour of the premises. If you're to do a lot of portraits, the 85L is superb, but what I like about the 135L is that you can frame the shots from far away and your model won't even know you took the picture. Both lenses are great, but which you prefer is up to your shooting style and how cramped the place is.
I really don't think the 24-70 measures up to two good primes, it get's the job done and your clients would probably be happy with the results, but the primes give you an extra edge and also gives you better bokeh and more possibilities with shallow DOF.
I always run two bodies, partly because sometimes you simply don't have 5-10 seconds to change the lens and partly because I need to have backup gear with me anyway, so why not use it.
Edit: for bodies I'd say 5DII are great, very good low light capabilities and the center focus point are not bad for these kinds of photos. Sure, if you can afford 5DIII's you'll probably gain a little bit but not worth the difference in price for this kind of shooting (in my opinion). I got one 5DIII and even though I love it and it opens up some new possibilities for shooting other things, I don't think it will be a major breakthrough for my weddings and events shootings.