My 11-year old daughter and I stayed at Jennifer's place while visiting DC and really enjoyed it. Jennifer was extremely accommodative of my questions while planning our trip and flexible to our ever-shifting arrival time. She had snacks and waters stocked in the apartment along with coffee/tea.
The space is terrific - clean, large, quiet. We could easily have fit another adult and child. The location near the train station made trips into the tourist area very easy. If you prefer walking- you could walk to the Capitol Building in 20-30 minutes, a couple of restaurants and grocery stores within a 5 minute walk and the Eastern Market and tons of restaurants/bars/shopping within 10-15 minutes.
We will certainly book it again when back in DC.