we stayed at a fairfield inn in the doral area just north of the airport. they offer free airport shuttle and charge 12.00 per room for shuttle to port.
www.tripadvisor.com
Great website!
Every hotel detail rated;
Lists specific information regarding shuttles and transfers;
Past guest recommendations/good or bad
I haven't stayed there yet but there are a few Days Inn in Miami have free shuttle from airport to hotel and free shuttle to cruise port it says. One says a third person from one room going to cruise port pays $10 . Not sure of the area but check Days Inn Miami International Airport, or other Days Inn in the area.