Keilen,
When I worked there, in the buffet they had lobster on Wednesday night and they also had a gourmet restaurant which served lobster, but there was no crab.
There is a wonderful seafood restaurant right on the beach called
Capitan Cook's which has every kind of seafood imaginable.
Ask for more details about it when you arrive at your hotel, it's about a 15 minute taxi ride and most of the tour operators have excursions which end with a meal at Capitan Cook's.
Buen provecho!
Michelle