For those who have done Boston to DC - I know that drive isn't too bad and actually flights can be pretty cheap (my neighbor actually teaches at Georgetown Tues - Thurs. She flies Boston to DC every week). I only went to DC once when I was 10 or 11 and just for the day passing through. I think we just did the Smithsonian. Do you think there's enough to interest active kids there?
Oh my gosh, yes! Plenty to do. We took our son during spring break a few years ago when he was 9, that was a perfect age. It's a very active trip, not a restful vacation, and if you have a week you might want to make it a combo with a few days in VA Beach or Williamsburg. But that's dependent on your family, your parents, etc. We stayed in National Harbor, in a timeshare condo, which was perfect. We drove from CT, it's a really reasonable drive even from Boston. National Harbor has stuff right there, a waterfront, cute shops, restaurants, some activities, etc. And our timeshare had indoor pool, movie nights, game nights, etc. right there, which was also nice for when we had some down time.
We took the metro a few times, but my husband preferred to drive and park near to our sightseeing for that day. We used Parking Panda app, and that was AWESOME. Ds's favorites were Spy Museum, Newseum. We all also loved the Udvar Hazy Air and Space, in Chantilly, VA. It's a short drive, and worth it! Gets you out of the city, lots of fun restaurants in the area. We got ds a National Parks passport, which was a huge hit ($6) and he was excited to get a stamp at each place we visited. (Almost all participate.) We enjoyed the memorials, did a tour of Arlington. On our to do list was Old Town Alexandria, which we didn't get to, there is a fun pub there (Murphy's) with trivia nights that I read were ok for kids and cheap meals, so that's something the family can do together. We did a tour of the Capitol, Library of Congress, National Archives. Lincoln walking tour.
We were tired at the end of our days on foot, so we enjoyed having the condo immensely. Several nights we did a fun lunch in the city, and then 'curbside takeout' at Outback to bring back to the condo, or got food 'to go' from one of the places (like the awesome crabcake place!) right in National Harbor (quick walk to pick up) and ate it at the dining table. Then had a swim or watched a movie. We wanted to have our shoes off!