When I travel, I get on IG and start typing in the place Im going and then whatever category and follow accounts from there. Its been really helpful for me in finding good restaurants and stuff to do. DcCheapEats is a good one I follow.

Someone suggested buying the scooters, definitely get helmets and be extremely careful shen riding them and with your kiddo. Drivers in DC are maniacs.

The Mall is cool, seeing all of the monuments and the Smithsonian museums is neat. Lots of walking/scootering and would need to take a few days just for that.

Going to a baseball game at Natationals stadium would be super fun for a family and so American. Can get snacks and drinks but definitely they're more expensive. You could also go to a Washington Commanders American football game if you'd like. Tickets are usually more expensive though.

Within an hour to 2 hours away you can visit Pennsylvania, Maryland, and Virginia. Fall is in full swing so you may be able to do some mazes or Halloween haunted houses, stuff like that In the more rural areas which would be fun for you to experience as well.