Can't help you in terms of rates, but I do have an experience to share:
We had 7 people in April in Orlando, and TTC picked us up at the airport in a 10 passenger van. The driver told us it was the same as the 15 passenger van with the back two seats removed to make it a 10 passenger. When I commented on it, he mentioned that when it is used for 15 passengers, there is almost NO ROOM for luggage!!!! With 15 people, that sounds like a BIG problem to me! Just FYI.
Patti