You have six companies to choose from for car rental in Port Canaveral. They are Avis, Budget, Dollar, Enterprise, Hertz and Thrify. All of them have free shuttle to the port and drop off service in Port Canaveral.
Well, one suggestion would be the Radisson Resort at the Port. They have free cruise parking with a one night stay and free shuttle to and from the port. There are 15 Port Canaveral park and cruise hotels in the area.