Well, I am glad to hear you are that close to Miami.
There is a really good site called travelmath.com
that will tell you exactly how much it will cost to drive to any port.
I am not sure where you are but from the northern border of FL to Miami can be about 400 miles - bigger than it looks, but still manageable.
It makes ME really happy to see that you can work this out, too, and in truth, for the best value and trip options driving to either Ft Lauderdale or Miami, will most likely give you the itinerary your dad has been dreaming about - (as opposed to cruising from farther north).
But, I would also still check on Port Canaveral, too. It is a lot closer and it has some really good cruise values right now as well. Might be the best choice in the end.