well, I've never stayed off site, so I wouldn't know this, but why would they take a reservation if the person wasn't allowed to be there??? wouldn't the CM at Disney Dining reservations specify that when taking the reservation?
so, it's just a matter of "transportation" to MK from the TTC?
OP,.maybe you could park at the poly, contemporary, or grand floridian. they Do allow parking for 3 hours for dining. but then you would have to go back and move your car in 3 hours.
or, heck (ready to get flamed), but since they took your reservation .. for CRT, no less, which you have to pay ahead of time.. I would drive to the pop century or all stars early, park in one of the huge lots, and take their bus to MK. ( I only advocate this because they took the OPS reservaton and credit card # for an 8 am seating)