We loved Chankanaab. We had three families. We saw the sea lion show, some of us swam with the dolphins, some of us snorkeled, and the children had a blast playing in the shallow inlet. There was something for everyone there. We all took a taxi (actually a van) to the park, and everyone had a very fun and relaxing time -- if that's possible with 6 adults and 8 children!!! Therefore, I would highly recommend this park.
Note: I read a recent post about a garbage/smell problem at the park, but we did not experience any of that and thought the park was nice and clean. Hopefully, that was a one-time occurence, and they've fixed the problem.
Enjoy your trip!