Based on all your inputs: Here's my rough itinerary:

Saturday

11Am pick up rental car from BWI, drive to Franciscan Monastery (tour at 12PM?). Spend some more time at the Basilica of the National Shrine of the Immaculate Conception

2PM- drive to willard and check in (any idea where to park with in-out privileges? Willard charges $42)

3PM: Visit Newseum.

5PM: Visit Madame Tussauds (my parents have never been to one)

7Pm: grab dinner to go (suggestions?), drive back to Willard, early dinner and rest.

8PM: If the monuments are still lit, drive around the national monuments, see the reflection pool.

If the monuments are not lit, what would be a good place to visit ~8PM?

Sunday

morning: stroll around National Mall/ Capitol Hill. See it by day.

10AM- check out and visit National Cathedral, drive by Georgetown, grab crab cake sandwich from CF folks

12Pm: Visit Arlington national Cemetery

1Pm start from Cemetery, drive to IAD and then to BWI (parents' flight from IAD ~5PM, my flight from BWI to west coast ~430PM)

Does this sound like a good plan? Would love your feedback about the itinerary and suggestions for restaurants to carry out food from.

Edited to Add: The times here are approximate. We normally don't rush; so a few of these can be skipped