Well, if you really want a scenic road, you really can't beat Skyline Drive, which takes you over the mountains and gives an awesome view of the Shenandoah Valley, though in the Summer it can be quite hazy from up there. I'm assuming you'll be taking this trip in the warmer months, as the road is closed in the winter.

Many of the roads around and through Gettysburg are quite nice, as well. I seem to recall an enjoyable drive on PA-34 from Carlisle to Gettysburg.

In Virginia, at least away from the cities, most of the two-laners are very scenic and enjoyable to drive.

Day 5 seems like it would be the most conducive to exploring back roads and seeing what is around. the Eastern Shore of Maryland; I have only driven US-13 in that area.

For diners - Wright's Dairy Rite in Staunton, VA gets my vote (again!!) Straightforward burger and fries fare, awesome shakes.

Of course, all of this depends on how much you wish to drive and how much you want to explore. Happy travels!