We always rent a car. This is always much cheaper when you have more than 2 people and works very well for us. We rent the car at the airport, usually only paying around $35 each way, I drop Nancy and the luggage off at the pier, drive to the rental car office (less than 3 miles away), then take the free shuttle back to the pier. When we come back from the cruise, we repeat the process. This way we're on our own schedule and can do what we want, when we want, and where we want.
And if you have never been to Cape Kennedy, you can plan your flights home late in the evening, then drive over and do a tour - it's absolutely amazing! Or you can spend a day at Disneyworld or do some shopping in Orlando.
Shuttles/limos are definitely easier if all you want is direct transportation, but the price can quickly add up when you have more than 2 people. We just had a family of 5 rent a minivan for $50 each way and that included a car seat for the little one.
Just another option to consider, but definitely stay away from the transfers offered by the cruise line - those are the most expensive way to go.