Chichen Itza is a grand excursion, but it is an all day event so some of your guests may not be up for it. The Tulum archaeological site is closer and can be done in half a day, a good idea for those whose guests may want to return early to the resort.
Xelha and other ecoparks are fantastic, but most likely your group would not stay together. If "bonding" and sharing the experience are important, you might look at private tours of some of the smaller cenote parks where you can keep the clan together, Aktunchen and Hidden Worlds come to mind. Xoximilco is a fun night experience, "trajineras" are specialized boats that do a canal circuit, guests are served authentic Mexican dishes, there is live music, games on board and lots of tequila. Your resort may be able to offer a private group tour on a catamaran or snorkeling excursion, always worth asking your coordinator for guidance too as so many hotels have in house tours that may end up being more economical.
If your guests have a mixed bunch of tastes, sometimes you may offer a couple of options, ie, golf outing for some, archaeological site for others, snorkeling trip for the rest. I do like the idea of doing something as a group though, makes the experience something special. There are SO many options that it can be tough to decide, I would measure your group's interests (and your own of course, it should reflect your taste!) and narrow down the list.
Have fun planning!!