Personally I must agree with the advice of SAS Transport Quality Shuttle
Service at Affordable Prices. They are great at only $15.00 per person and have always expedited getting many of my friends and myself and family to vessels. SAS recently upgraded their service to include reservations service to include Android and I phone services.
While utilizing Carnival Cruise lines service is an option (and they will take care of you if the flight is late - phone ahead if possible to hold ship) it appears you have coordinated your schedule well. At the end of your cruise I recommend you relax and leave the negotiating to Carnival and go see my friend Allie Alligator by booking the return transfer with Everglades tour.
It can be booked one way and you can utilize SAS to expedite you to the ship and get on wind down, relax, and enjoy lunch on the day of arrival. I trust your agent or professional travel concierge told you about Carnival's Faster to the Fun
as it is per cabin and not per person and truthfully worth it unless someone in your cabin is a VIFP Club Platinum and/or Diamond member like myself.