We went on our first Disney cruise back in November and we had a wonderful time. If you don't see yourself as shoppers, then I highly recommend a time when the ship docks @ Castaway Cay twice (also known as "Double Dipping"). Ours was a 7 day cruise which stopped @:
Castaway Cay
Grand Cayman
Cozumel
again at Castaway Cay
We didn't want to spend too much of our time shopping so we instead planned excursions that the family enjoyed. While at Grand Cayman, we visited Boat Swains Beach
http://www.boatswainsbeach.ky
The general admission fee allowed entrance to most of the park and an additional fee would include being able to snorkel in their lagoon. We had a nice time, but found that the lagoon was extremely murky and made it hard to see beyond 15 feet.
At Cozumel we visited Chankanaab Park
http://www.cozumelparks.org.mx/
Had more fun here vs. Boat Swains. The admission included snorkeling gear and it was nice being in the open water vs. a man made pool.
There is also a beach designed for kids closer to the front entrance, but I must advise you to bring water shoes or water socks with good souls. There are some fairly sharp rocks leading out into the water. I saw many folks who experienced hurt feet when they waded in barefoot. There are walkways into the water made of sandbags but it you can easily slip off and land onto something uncomfortable.
Castaway Cay was amazing. We took in the Sting Ray experience and our son was the most excited to feed them. Afterward you could snorkel with them in a designated area. We also rented bikes for the tour around the island. Disney thought of everything: the roads are nearly flat everywhere so it was easy to pedal around. You even get to bike on the old plane runway. There are multiple watering stations along the path too.
Parental tip: If you plan to have your children utilize the Kids camps while on board, I'd advise registering them while at the terminal before boarding. There may be a line, but you're most likely going to wait before going on the ship anyways. And there were 6 CM's helping with registration vs. only 2 on board.
We brought our own mini-medical bag just in case we needed it: children's pain/fever meds, something for a queezy stomach, etc.
If you plan on attending any character meet-n-greets be sure you arrive early or else the lines get super, super long. It seemed that folks took their sweet time while seeing/taking pictures with the characters and made the queue increase exponentially.
