I'm assuming MVAR is the "7-Passenger Minivan" class. If so, I was in MCO last month and looked at Alamo's selection in this category for a future trip.

There were about 8 minivans available when I looked. 5 of them were Dodge Grand Caravans and 3 of them were Chrysler Town & Country. I also looked at National's minivan section as National shares car inventory with Alamo (and I think Enterprise as well). National's minivan selection was smaller at the time, with only 3 Dodge Grand Caravans and 1 Chrysler Town & Country. I think the odds are good that you'll end up with one of these at MCO. I can't speak for ROC though.

Good luck with the rest of your trip planning!