Camp Carnival is open on port days. They have some rules and guidelines for parents who wish to leave their children on the ship while they are in port, I don't recall exactly what they are (we usually take our kids off with us) but I know that they have some extra comments and rules. Camp Carnival will also feed your kids if they know that you are off on an excursion, but if you are on the ship, they expect you to come and get them.
In addition, the hours are different on port days than what they are on sea days.
Wish I had better details, but for us, a port day is a day of exploration, with kids in tow : )
Thanks 2littletime. This is the first time my daughter and children have sailed and we are gathering as much information as we can to make for a pleasant trip. The boys will be 6 and 9. Excursions haven't been checked yet. Thanks again.