I have been on the Dawn once before in 2006 and we are going again next week. In looking at the deck plan and from my own personal recollection, I believe that the partial obstruction is from either the lifeboats themselves or the arms that suspend the lifeboats. The lifeboats are suspended above deck 8. (see the deck plans on NCL.com).
As far as the question for the kids, the ages that you note are kind of in-between and it could be hard to guess if there will be a lot for them to do. For the younger ages, there is a lot to do because they have an organized kid's program. Once they get into the middle-teens, some kids don't want to be in with the "babies" and depending on how many other middle-teens there are, it could be good or bad. There is usually a teen disco available but there again, the would include some of the younger kids too. They have a video arcade but that can be as expensive as the Casino, if you know what I mean.
Off of the ship, I am sure that they will have a lot of fun on excursions. The day at Great Stirrup Cay is basically a long beach-day. They also have beach volleyball and soccer on the island.
After I return from my cruise, I will update this thread with any other information about the kids program if I see anything that is worth mentioning.
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