OP here, I looked online and the Smithsonians have wheelchairs available to borrow, so we’ll try that if needed.

How recently? A walking boot could really help and be good enough for museums etc. You could also get a wheel chair.

arena theater/ free shows or reduced shows at the kennedy center. Parking is expensive. Wharf; dine outside on the waterfront; expensive. as is parking. There's a water taxi...check out it's route; maybe that's interesting. There is a hop on bus. It sells tickets near the Ford's theater which is where you can park.

My brother is coming for a long weekend soon, and I recently sprained my ankle and am supposed to take it easy. I was thinking we could do a bus tour or a boat tour together. Any other ideas of stuff we could do together that wouldn't involve much walking or standing?