And while you are at it plan your trip to catch a game in Baltimore when the Sox or Yankees are playing . And on the way back , hit the Baseball Hall Of Fame in Cooperstown NY.The ride to Gettysburg from NH is only 8 hours. Drive to Gettysburg, do that for a couple days. Then drive 2 hours to Washington DC, walk the Ellipse, see the White House and Capitol, visit the Lincoln Memorial. From there, head to Skyline Drive and drive south down the Blue Ridge Parkway. You will hit Gettysburg, Washington, and see some of the most incredible places on the East Coast. The ride south on those roads can be slow, so you can take 95 back north and be home in a day. While you are down there, go to Charlottesville, VA and stop at Monticello.
The reality of most road trips is that while you are on the trip, everyone is miserable and fighting, there is never enough time to see everything, and tempers flare. When you look back on it years later, all the bad stuff gets forgotten.
When I was a 10 we drove from San barnadino near where my dad was stationed to Dade city FL close to where he transferred to McDill AFB in Tampa, we took a travel trailer and about a month, have also been from GA to MI several times as an adult .I like driving but I always try and avoid major cities..