Agree that they should focus their search on somewhere near you. With that said, my inlaws have really enjoyed living at King Farm and there are certainly options within your folks' price range, like
https://www.redfin.com/MD/Rockville/111-Watkins-Pond-Blvd-20850/unit-3-201/home/10554369
It's not a 55-plus community, but most of the people in their complex (there are several different condo associations at King Farm) are in that demographic. They like the nice landscaping they don't have to maintain, nearby grocery store, and the shuttle to the metro when they want to come to DC. And many of their neighbors have moved to Ingleside or other nearby independent/assisted living communities as their needs have grown, so it's nice that they didn't have to go far away.