My wife and 4 year old DD booked a Dolphin swim tour through
DCL at Chankanaab Park in February 2003. There was actually no swimming at all, just wading in waist deep water. There you get to pet, feed and kiss a dolphin as he swims by you. The DCL program has little or no age limit.
My wife was disappointed with the DCL dolphin program, but I was much relieved since I am not a strong swimmer.
Chankanaab park also offers programs where you *do* actually swim with a dolphin, but it cannot be booked through DCL. This program is similar to Discovery Cove program which has an age limit of 8 or 12.
If you have small children, do go to Chankanaab park and enjoy the beach, but skip the DCL dolphin program. If you want to pet a dolphin, stop by the dolphin pool at Seaworld, where Dolphin petting is included in your admission, and you don't even need to get into the water. It's also MUCH cheaper for almost the same experience!
If you have older children, then book the full dolphin swim at Chankanaab Park (not available through DCL) or spend a day a Discovery Cove.
-Paul