If you get picked-up at the Grand Hyatt at 8h, you won't be back at noon. This is not efficient. If you get a driver to get you to the Mutianyu section of the Great Wall then go from the airport as it is in the same part of town. Then you can be back at your hotel for check-in before noon.
You can have time to cover several places in the afternoon. From the hotel you can walk to Tian'Anmen and the Forbidden city.