no idea how they do for weddings, but I stayed at this Adults only resort (I think 16+) and I would go back in a heart beat
http://www.realresorts.com/The-Royal-Playa-Carmen/
I have been lucky enough to stay at my fair share of resorts, and I loved this place.
It is large compared to your Cancun resorts, so more walking, but in town, so not massive, which can be a pro or con.