We've traveled to/from DC a couple of times with our fiver from/to Northeast Indiana. Our preferred route is east on I-70 out of Indianapolis. I don't believe that there are any grades on that route that your rig couldn't easily handle. Not sure where Shelby Township is in Michigan, but if it's in the lower peninsula, you wouldn't be going too far out of your way to get to I-70 via I-75.
I don't have much to add to the suggestions others have posted regarding things to see and do beyond recommending the Antietam battleground as a great day trip. Cherry Hill is the best place to base yourself, IMHO, given it's easy access to the metro. It is a bit pricey, but worth it unless you're running on a very tight budget.