For an almost car free ride (few roads to cross, car free trail$, there is the W&OD trail (https://www.novaparks.com/parks/washington-and-old-dominion-railroad-regional-park). You can ride 45mi out to Purcellville VA, so a 90mi ride total. Alrhough I would recommend to start further than Shirlington as the first 10-20 miles could be crowded.
I plan to join some of the WE group rides with DCTC MoCo Mafia group which I think is also with Potomac Pedalers. Can’t wait for warmer weather to get some outside rides!