With that big of a group, I think your cheapest transportation option is renting a day car. We did a day rental through Budget Rent-A-Car. When you get off the cruise, the baggage people will help you move the bags to the line for Budget (and other rental shuttle pickup areas). Budget was there when we walked up. And their office is very close to the port.
We also had a huge amount of time between getting off the boat, and flying home. However when we got to Budget, we called our airline and found out that if we made it, we could get on a 11:45 a.m. flight! This was at 10:20 a.m. We drove quickly from Budget to the airport (45 miles), switched tickets, checked in our luggage, returned rental car, made our way through security, and pretty much ran to the terminal. lol We made it just in time.
Our original plan for spending the day was to go to the Kennedy Space Center which is near the port. We were so pooped out though when we got off the cruise, that we were more focused on getting home at that point. We were happy to be able to get on that earlier flight.
Have fun!!!