Thats's a good question!
If your going on the cruise that we are going on on August 22n, it's probably to late to e-mail Carival to ask them. My first thought is to try calling them, they might have some suggestions for you; wouldn't hurt to try. Second thought, wait till you get on boat and ask.
Pot Luck: I wonder if the bus or shuttle that Carival has to take the excursions to the parks might take you for a fee, if they have extra space on it?
I'm just letting my brain ramble with thoughts on this, sorry!
Good luck in finding the answer to your question and have fun on your cruise!