Just returned from a Disney Cruise on the Magic (7 nights) and I offer an alternate view to what everyone else is saying. First a brief: Married male, twin 5 1/2 year olds, live in Northeast, wonderful wife.
PLUS SIDE - Disney crew is a well oiled machine. Fantastic on EVERY level. The service is wonderful and the disney characters are nothing short of fantastic. How these people stay so patient and up beat is beyond me,... but they absolutely do. My hat is off to them. Fantastic job. 10 out of 10 stars.
The ship is in perfect condition and the crew works hard to keep it that way.
The other people (cruisers) on the boat are also a pleasant plus. EVERYONE is in a good mood. Very polite and happy overall.
DOWN SIDE - Imagine living in a walk-in closet with 2 kids for 8 days and you get the idea.

We had an outside stateroom on deck 6, mid ship. Very nice room but not large. This also means a total lack of privacy. Simple things like getting changed become an adventure.
The child care is just o.k. It is available and the facilities are nice. However, in my opinion it lacks structure. Imagine puting fourty 3 to 5 year olds in a big room with no one person in control and you get the idea. There are people to attend to the kids but the ratio is about 20 to 1. Besides the fact that most of the time the supervisors were congregating around the front desk while the kids just ran.
Other minus is that about 30% of the computers (video games)were off line. Once again, imagine giving kids computers with little or no supervision and you get the idea. Doesn't take long for default messages to appear,....
Bottom line - Don't fall for the hype that it this is total relaxation. Remember, you are still on a ship with your children (and several hundred others)and sleeping in a closet. It is exactly what it should be. It is a FUN time for the WHOLE FAMILY.
On the last day of the cruise the women in the cabin next to ours put it well. She said - "I thought this was going to be totally different,... THIS WAS WORK!"
Would I do it again? In a heart beat. But 4-nights, not 7. But my hat is off to Disney. They define efficiency.