I looked at Moon Palace and Gran Caribe too. Azul Sensatori is a resort my travel agent frequently recommends to her brides. There are some pictures on her site:
With a group of 80+ people the rooms available at the convention centre of the Iberostar would be perfect! They have large rooms with glass walls overlooking the lawn and ocean in the background. Paula the wedding coordinator there has been really pleasant to deal with.
I also looked at Barcelo Maya but didn't like how large the resort was and that it was on the Mayan strip, I preferred the Cancun strip (wide beanch and miles of it for people to walk!)
If you search for "Del Sol Photography" on this forum they have a post with links to TONS of weddings they have photographed all over Mexico and you'll see the resorts and types of pictures/locations available at each.