I don't know if you have picked a location or not, but I would contact Patricia with "Weddings in Cancun". She has access to a private beach, which matches the description of what you are looking for. She is so great to deal with. I decided to do Xcaret for the ceremony and a reception at Blue Parrot, but the "Playa del Secreto" was my second option. It looks beautiful!
Tell her Jessica gave you her info. on bestdestinationwedding.com, so she knows how you found out about her. Patricia's email is doves at weddingsincancun.com .
Also, her prices are very reasonable too!