We did the Mexican Cuisine Workshop which is also at Playa Mia, and includes some free time to enjoy the resort.
We are not much for beaches, but it seemed nice enough. It was in October and the place was not crowded at all. I would say that the beach is pretty gravelly, but there seemed to be lots of chairs, umbrellas, and toys available. the food they had was OK (we didn't really have any because we were there to cook our own) and the free drinks were a nice bonus. All in all it was a pretty well run, clean, and friendly place.
I highly suggest the workshop for those without young children. The chef, Luis, and his assistant are comic and culinary geniuses and we all had a great time cooking yup some authentic Mexican cuisine. We then had a great time eating it with our fellow "cooks".