Hi we have just done the same journey ourselves and it took roughly 4 hours with a short stop at services. The ships are listed by number at the entry to the port so easy to follow, also with the size of Enchantment you will probably spot her from a distance. Do you know there is a multi story car park opposite the terminal and the cost is $15 per day. You drive in to the terminal drop your bags with the porters and cross the road and park, its that easy. Enjoy!
The drive will be a good 4 hours each way.
For the transfer to the Port, check with your car hire company, as they usually offer a shuttle from the airport drop-off to the Port. We used Alamo & they do this in both Fort Lauderdale and Miami.
Allow a full day for each journey. The roads are very good, but it will take you at least 5 hours each way. There is no difficulty at all in finding the ship once you get to the port area. It will be well signposted, and there are plenty of people around to ask.
Best wishes, Coli.