Where do you live? The drive to Shenandoah can be long. There are a good number of local trails where the leaves are changing that you could get to more quickly and then go to lunch. We were at Scott's Nature Preserve last week and saw the trees starting to change. You can hike down to the Potomac and see the trees all at once. Or go to Great Falls. Manassas Battle Field has a bunch of great hikes that go through the woods so you can see the leaves, get in a nice hike, and get in some history. And there are a ton of smaller places you can pull over for lunch and the like.
There are some great hikes in Shenandoah and lots of small towns that you can stop in. Front Royal has a bunch of different areas to stop but I am not sure what is open now and what has shut down because the Summer Season has ended.