ITA with tuckermom, with the age of your children they will not have a lot to do and you are there until at least 2 p.m. when the first ferry returns to Nassau. We went and did the Dolphin Encounter and then my kids played in the water and the beach, but they are 13, 11, 9 & 6.
We were the only cruise ship there so it was not crowded, but then again not much to do.