Hi Robyn,
Unfortunately, the Boston-DC corridor is not the most scenic for a drive, and the direct routes vary between boring to downright ugly. You can get nicer drives if you take a really circuitous route (for example, from Boston, take Route 2 all the way to the Albany area, the southwest toward Allentown PA, then south toward DC), but that will involve a huge amount of driving, maybe twice as long as a direct BOS-DC trip.
You might consider the train as an alternative to flying. The Amtrak service from Boston to DC is about 6.5-7 hours, and the scenery is often quite nice. I'm only familiar with the Boston-NY portion, but you'll get numerous glimpses of the ocean and marshes, and you have an excellent view of Manhattan as you make your way in from the western end of Long Island