Just got back in Feb. What a wonderful place. We took the excursion from the ship. I think the cost was like $35 each but you got on a nice A/C'd bus which runs every 30 minutes from the port to the place. If you are going to Xcaret from t Playa Del Carmen, then the trip is literally a few miles (10 minutes on not so great roads). Once there, there is a ton to do and you wont be ablt to do it all. If you plan to do the dolphin encounter, go early and get your tickets right away. There is limited space and it fills up quickly. Its pretty cool but at $115 per person, its a once in a lifetime for me.
There are like 10 restaurants in Xcaret. They range from basic fare for $5-10 to buffet for $20 per person. I highly recommend the LaLaguna buffet but its the most expensive ($20 per person) but man was it good. Still figure $50+ for lunch for family of 4.
Snorkeling is free. Not sure what the rental price is for gear. Take good walking shoes as this place is HUGE!!!. And there are not motorized transport that I could find. If you get tired, simply find any of a thousand jump off points into the man made lagoons and rivers and cool off. you can even snorkel through an underground cave.
One nice thing, you can go back and back to this place and never do the same thing twice.