We arrived this afternoon (Thursday) and We  plan on seeing some sights tomorrow afternoon and Saturday before leaving Sunday morning. Will be around the embassies tomorrow morning until noon getting my wife's Dutch passport renewed. Then we can head out to sight see tomorrow afternoon and Saturday, all day. I definitely want to see the Air and space museum, Lincoln Memorial and Washington Monument. The tomb of the unknowns and any other big ones you can think of that we might want to see. We have a car with us, but realize that is a mistake.

Any suggestions from locals?

Go to the National Mall and see the Smithsonian museums. Also, the Newseum is good. Smithsonian are all free. Grab lunch at the Hawk and Dove, or some place on that strip. Food in the area is good. Go see your congressman. Sometimes they have coupons, brochures, and other sightseeing tidbits. Might even get to see his office, see the chambers of the House, etc.

Mt. Vernon is close enough to drive to.

The Jefferson Memorial?  Ford's Theater?  I love both places.

ETA:  Just realized I'm a couple months late with my response....

Just so you don't feel bad, about being late to the ball.

think about getting a Metro Pass, lots of places close and easy.  Avoids parking

Based on past trips, not surfe how reliable Metro is these days.