We are heading down in Aug...staying at BWV for 6 days, then renting a car and driving to Port Canaveral for two nights before our cruise. When we get to port, we'll return the car. Then, most likely we'll use
DCL bus to get us to the airport. In your case, I would be tempted to price out a rental for the trip to port, keeping it and driving to WDW and returning it there. Or taking it in two sections...one rental from the airport to port, return it there. Then rent a different car for the trip back to WDW and return the car there.