[bluesunset99]

I'm sure they'll be more, as a lot of families tend to travel around Xmas. Although it is a tad expensive, swimming with the dolphins is always a good bet, I did the horseback riding myself when I was in Mayan Riviera just a couple weeks ago and loved it! It was at the Rancho Loma Bonita, you get to swim with the horses for a brief time too, bareback, on a beautiful beach. It was $50US and may or may not include transportation, depending on the hotel I believe.
Taking a trip into Playa del Carmen for shopping is another option, tons of things to look at and buy I could have gone there another day to shop but didn't get the time, I only spent 4 hours.

If there is anything you'd like to know, feel free to ask.