Just out of curiosity...why would you want to go to the parks before checking in? I have only stayed in Deluxes, so can you not leave your luggage at the Moderates or All-Stars?
It just seems a bit out of the ordinary not to swing by your resort, check-in, leave your luggage with the bellman, and then scoot over to the parks without having to worry about unloading the car later after a day at the park. Who knows, you might get lucky and your room will be ready.
Brian