Hi Minkydog! I'm glad to see you are thinking about this trip- it sounds like a wonderful opportunity to see your family.
When DD and I went to DC, we stayed at The George. It's at the Capitol building end of the mall, in the Union Station area. In fact, we took the train into and out of Union Station, and we walked to the hotel. It's a small boutique hotel. I don't remember what we paid for it, but I got it on Hotwire. I am not sure that your DH could actually walk to/from Union Station and the Mall area, but it's close enough that cabs shouldn't cost an arm and a leg. We walked the area safely after dark (not too late, but maybe up to 9 or 10 pm) and there were quite a few cafes and restaurants in the neighborhood, IIRC. Also, I have friends who stay in the DuPont Circle area as subway access to the Mall is pretty convenient. She said she's always able to find a deal on chain-brand hotels for around $100 a night, give or take.
Something I learned after DD and I wore ourselves ragged walking the Mall from museum to museum, monument to building, is that there is a shuttle bus that traverses the Mall loop, and I want to say it's free
or maybe only $1 per ride. Something to keep in mind.
I know I haven't given you a lot of concrete info here, but maybe it's a jumping-off point. I am sure you'll get a lot of help here; I posted a question about getting to and from Manhattan from JFK and within a few hours had plenty of first-hand info to pass on to my DD. I just love the DIS-folk! Good luck with planning your journey!