I don't know what to say, we are taking two months just to go from SC to NM and back home through the southern part of Texas. So much of what I would suggest might not be of interest to our friends from the north.
I would suggest you avoid I-95 at least in the North East. Anything north of Richmond VA is pretty much a major headache.
If you can work it out - Washington DC is worth a few days. The museums and monuments are amazing. We plan to make a stop there next summer.
Perhaps angle west from there and head down to I-40 and head west. That will take you all the way west to AZ. Perhaps when you get to Arkansas head north to Tulsa and then follow some of the old Route 66. On other posts I read about the Cowboy Museum plus there are a number of museums about our native Americans. When you make the turn to head back home, some folks on here can make recommendations on which National Parks are good options as you work your way north.
Good luck and let us know your plans.
Looking forward to new adventures and new friends.