Mindymom,
We had the same issue in December. We stayed at WL for two nights before heading for the port, and then spent the rest of the day after disembarking at DTD until our flight left at 3:00 p.m. from MCO. We had separate rentals each time. I finally decided to rent a Ford Explorer, I guess because I have owned 4 vans, drive an SUV now, and that is what I am used to. It seems like once you finally get out of a van, you don't really want to go back!
We had two adults, two teens, 5 suitcases (one had our Christmas decorations and gifts in it) and carry-ons. My own personal car is a little larger than the Explorer, but I compared the size of the cargo area online, and figured it would be okay. Everything fit well in the Explorer, the car was very nice and roomier than I had expected. There was plenty of room for one more in the back seat.
We rented through Budget, had a brand new Explorer both times, and enjoyed it very much.
In fact, if the engine was a little bigger (it was a 6 cylinder), I would consider buying one!
Hope that helps!