Sorry I can't help beyond offering this suggestion...
You can rent a car while at WDW. There's an Alamo/National Car Rental Center on-site, just outside the entrance to MK. Either the Car Care Center OR Guest Services should be able to help arrange to get you to and from the center to drop off or pick up a rental car.
Why do I mention this?
Because unless the Pop Century is totally booked on 8/26 (which is admittedly possible), you can book your stay one night earlier, fly in to MCO, use Disney Magical Express to get to Pop Century on 8/26, wait a few days before you get a rental car, return the car the night before you leave WDW, and use DME to get back to the airport.
And the extra money you lay out for one more night at WDW could, conceivably, be absorbed by the money saved by only having a rental car for part of your trip, rather than the entire trip.
EDIT: I stand humbly corrected. Though you can book cars while at WDW, it seems that the airport rates are significantly cheaper than if you book while on-site at WDW. It doesn't look like you'd save any money using my logic. But it might still be easier...