Six of us went on this July 4 sailing, my wife and I and our two kids (6 and 2) and my parents. We had two separate staterooms not joining.
This was a very good experience for the six year old. The Disney Adventure Club is extremely well run--its a place where kids over 3 can be "checked-in" securely and where they have games, movies, and other activities all run by a well staffed and well trained crew. Simply fantastic and a huge draw for this cruise. Actually the biggest draw in my opinion.
We used the nursery twice for our 2 year old. It too was very well run, and the customer service is exceptional. We received little pictures and notes from the nursery staff documenting the 2 years old's visit. Fantastic. The nursery is an additional charge, however. So that's the first thing I would do differently: I would wait until my kids were over 3, and thus eligible for the free Adventure Club. Or, quite honestly, I think the ideal age for kids would be in the 5-8+ year old range. Kids in diapers aren't allowed in the pools, understandably so, so it's best to go with some a bit older. Other than the nursery there simply isn't any real "programming" for kids much under the age of say 4 or 5. And that is surprising to me, considering this is a Disney product.
Cramped with 4 people. We were about the strangle each other on the last night.