So these are the things we ended up doing in D.C. for the week:
Sunday: Newseum (not crowded on Easter and no school tours, interesting but not fantastic)
Monday: Planned, but canceled U.S. Capitol Tour (due to gunman from TN). Improvised by hopping on the Circulator bus and visited Jefferson Memorial, FDR Memorial, and MLK Jr. Memorial. Tons of cherry blossoms everywhere! Drove to dinner in Arlington, then to U.S. Marine Corps Memorial/Iwo Jima Memorial at night (really beautiful!)
Tuesday: Natural History Museum (too crowded), Air and Space Museum (too crowded), U.S. Botanical Gardens, National Art Gallery (east wing, west wing was closed for renovation)
Wednesday: National Postal Museum (quiet, nice), attempted Lincoln Memorial at night but could not find adequate parking so drove around monuments instead
Thursday: Ford's Theatre tour, doctor visit with DD in Georgetown and good test of our Metro skills, DH and DS went to Smithsonian Castle and Freer Gallery of Art
Friday: National Archives docent tour, Arlington Cemetery with tram/trolley tour
Saturday: Udvar-Hazy Space Center, and antique shops in Maryland
Our weekly SmarTrip cards worked well for $36 each
. We only went over 5-10 cents each so still have a small balance on each card. Ended up keeping the rental car and used it to pick up pizza, drive to the U.S. Marine Corps Memorial and Arlington at night, and to drive to Udvar-Hazy and Maryland on our last day before flying home. Put 130 miles on the car.
OTA was great, love the location and the staff is super nice and friendly.
No plans to go back with the kids again, I think they have had enough of museums and touring, but I would love to go back to see Mt. Vernon and other sights that they were not interested in.