A Princess transfer really doesn't sound like an option. Transfers are usually from the airport to the pier.
Find out if the hotel provides transfers and if there is a charge. If they don't have a transfer or the cost is high I would just call the front desk, before checkout, and have them call for a minivan/SUV taxi to take you to the pier. You might have a bit of a wait but you will be able to get one that will handle four people and a reasonable amount of luggage.