I am in a guaranty 12 so I have no idea where I will end up. I have had the sideways cabin, but on the 6th deck, I LOVED it, it has a bit more floorspace. I am hoping for a Cat 11 upgrade, but I am going to be happy in the bowels if that's what I get.
Since your kids are young, they can't go to the spa or Palo. There are a bazillion activites to do for kids on the ship in the clubs, there is a pool slide at the Mickey Pool, both kids will have a blast, I am sure. I can't advise on shore excursions, I generally do not get off the shoip in Nassau (been there 12 times) and plan to do nothing at Castaway Cay, however, there are lots of tips on the board for family activities in Nassau, and the family beach at CC is gorgeous. There are club activities for the kids on CC, also. GO to the sticdky at the top of the board and look for the links to the Navigatiors, that will give you a good read on what the kids can do.