Try hotwire.com. I was just on there and they have a minivan that can be rented at the Orlando airport for $391.
Does that help?
Minivan
Features
Automatic Transmission, Power Steering, Air Conditioning, Air Bags, Anti-Lock Brakes, Cruise Control, AM/FM Stereo You're guaranteed a car from a major car-rental agency: Alamo, Avis, Budget, Enterprise, Europcar (International only), Hertz, or National. You save big because you agree to learn the name of the car rental company after you book. Once you make your booking, we immediately complete your reservation and show you the rental agency name and details. Miles
Unlimited Seating
7 adults
$391 09
includes all applicable tax recovery charges and fees