If you are flying in the day of the cruise why not use Carnival shuttle service to the port? It is not a long stretch from the airport to the port anyway. Less than an hour. I am not sure of the price on that. There will be people from Carnival there to meet the planes and direct you to the transportation.
“Twenty years from now you will be more disappointed by the things that you didn’t do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover.“