Would love the pups to run free.  Thanks

You can run your pup off-leash at Congressional Cemetery, about 25 acres. There is a fee of $10 if the caretaker sees you and doesn't recognize you as a regular. You can also sign-up to be a 'member', but there is a not so surprising huge waiting list.  

Battery Park near Foxhall Road

There is one on Calvert St. Not very grassy though so they might get dusty.  

Map of DC area dog parks + several review sites.