If I read it right, your hotel is on Miami Beach. The MIA is not too far from Miami beach. It probabley cost $40/taxi. You will need 2 taxi for your group. The other option is to find out if there is car rental near the hotel. If there was one, you can rent a mini van from the airport for a day and return it at the agency near the hotel. The taxi from MIA to the cruise port is $20.