Hi Donna!
Congratulations on your upcoming visit to Walt Disney World, just a few short weeks to go! You didn't say where you would be dropping the car off, so I am just going to assume that you will be dropping it off on Disney property. If this is not the case, please write me back with my name in the question and I will be happy to help!
The
Walt Disney World Car Care Center services National and Alamo, the hours are typically Mon-Sat 7am to 7pm and Sunday 7am to 5pm. While you are able to return your car after hours, the shuttles offered at the Car Care Center will have stopped running that late in the evening. While you could call a cab or change your return time to when the center is open, I think your best bet will be to return your rental car to the Dolphin Hotel.
Disney's Dolphin Hotel also has a rental counter for National/Alamo and with the Dolphin having Disney transportation, this would be your best option. In order to reach your resort, you will need to take a bus from the Dolphin Hotel to one of the parks that will still be open that late or Downtown Disney. After, reaching the park or Downtown Disney just transfer to the Art of Animation bus.
I hope this helps and please let me know if you have anymore questions!
Mandy