NCL's ship's generally have great kid's facilities, rivaling, if not beating out RCCL or Carnival in my opinion (I am talking about the actual kid's facility, not the people who work there). HOWEVER, I have experienced terrific Kid Crew Workers on NCL and then there are the others, that did not impress me in the least. They do pretty well on Sea Days, when issues arise it usually seems to be on port days. On Carnival and RCCL you know that their services are available to you if you should choose to use them at your convenience as long as it is within their scheduled hours. That is not generally the case on NCL, first of all you are charged hourly on port days for babysitting services, they do not have scheduled activities, and you are generally expected to sign up for the times you will need their services the day before and if you have the unmotivated slacker kid's crew, we did on the Pearl, they can be quite creative at finding ways to get out of watching children. They made it pretty clear the last place they wanted to be, is doing their jobs in the kid's club on a port day.
The hourly charge doesn't bother me that much, since on NCL you are only charged $5.00 per day for tips, but on other lines, I like the flexibility of being able to utilize the kid's club at my convenience, and the fact that other lines don't charge at all on port days and offer a superior experience for the kids with actual planned activities instead of just "babysitting", they could score big with families if they would fix this.
Now that being said, if having great activities scheduled on a port day is important to you, I would ecourage you to select a different line than NCL, but if that is not an issue, then NCL will likely be fine. Their newer ships are lovely and have lots to offer but it all depends on what is important to you, and what you expect out of your cruise experience.