Consider the cog railway at Bretten Woods in New Hampshire. Your kids will love the train ride up to the top of Mt. Washington and marvel at the heavy chains used to hold the roof on the buildings. This is where the highest ever wind speeds were measured in the US. Head on over to Acadia NP in Maine and soak in the scenery. Take a boat ride and go whale watching. Stay in Camden Maine at the state park, and take some hikes for fantastic coastal views. Stay in a campground near public transit in Boston, and check out the historic venues in the city. Tour the USS Constitution in the harbor. Just a few things that come to mind. Safe travels.