Just some comments on Pennsylvania, three spots that may interest your kids:
Railroad museum I haven't been but I know some people who have and they really liked it.
Hershey Chocolate world This one we have visited, I was underwhelmed but I'm not the target audience. You kids probably will like it.
And no link Gettysburg battle field, a real cut above other national battlegrounds from what I've been told. I haven't been there but it's on my list if we ever make it back into that area.
These are all in the eastern part of the state. One other thing the popular spot to stay at for DC is Cherry Hill CG in Maryland. They have buses that go into the Metro station that take you right down into the National Mall. They sell passes right in the cg office.
You do NOT want to drive into DC or NYC or Boston for that matter. We stayed across the bay for Boston and rode the ferry into the downtown area.
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