We used FLtours.com for that same route. Wasn't cheap but our driver was very good.
We do like a rental car, though. DH is executive with National, so we can often get a free day. Get it at the 4 Points Sheraton near Wet and Wild, drive to the port rental car place, drop it off, shuttle to the port. And then the other way at the end. SOME will find that renting it the whole time and parking it is cheaper than what we've done. We have not found it to be cheaper (again, we often have a free DAY...just a day, not a week). But with car rentals the only absolute is that there are no absolutes.