You really have 3 choices...
1.Use the
DCL transfers at about $65 pp, r/t.
2. Rent a car...may be up to $50 for one day, each way. That means dropping everyone, and the luggage, off at the ship and driving to the car rental office and returning the car. Then, take a shuttle back to the ship....be sure your rental company offers this. Then, off the ship, shuttle back to the rental company, re-rent a car, drive back to the ship and collect the group and luggage. Or, rent a car for the duration, pay to park at port, and drive back, as soon as you disembark.
I usually rent a car, pay to park at port since it's so darn convenienent. Parking is about $15 a day.
3. Hire a car service for about $250 or so.