Disney transfers: $39 pp each way. No car seats needed.
Private Transportation: lots of companies to choose from. People have used Happy Limo, Florida Tours, Mears. About the same price as Disney transfers if 4 or more in your party. Will provide car seats.
Uber: a little less expensive than private transportation.
Rent a car: least expensive option but have to pick up and drop off car. At Port Canaveral the rental car agency is a few miles from cruise terminal. There is a free shuttle services from the terminal to the rental car agency