Thanks for all the replies! All good points and I am taking each one into consideration.
I really don't like shooting the 17-40 @ f/4, as Kbmelb said there isnt much subject isolation.
Now, my 70-200 @ f/4 is not only sharp but provides decent background blur too. I guess the 85 can provide any further shallow dof stuff I need. Possibly stick it on my 7D, instant 135 (close enough!).
When walking around I think I could get some nice candids with the 35. Plus what usually happens is that someone else wants to join in the picture and next thing you know its a group shot! Yeah, I'm thinking 35 now! Plus I can switch it on to my 7D if I need that 50 ish look.
My plan is to use two bodies. Stick my 17-55 on the 7D and leave it there for any type of shot, wide or portrait. Then on the 5D I'll have my 70-200 for all the tele shots. Might keep an 85 and 35 handy or nearby to swith around on the 5D during the reception.
Somehow I a voice in my head is still nagging me "this is your chance to get the 135L and you're buying a Sigma lens instead?" Shut up brain I know what I'm doing.
Update - went out with my 85mm and experimented with it wide open on the 7D. Really like that focal length equivalent (135) but didn't like the purple and green fringing. Next tried the 85mm on the 5D II also wide open and there seems to be considerably less purple and green fringing but the focal length isn't as pleasing (feels too standard) Might sell the 85 and just buy both lenses.