Since this is your first time you will see all the things you should on a 1st trip but, many people miss two beautiful site:
Eternal Flame at JFK memorial and grave. The view is incredible
Women In Military Service For America Memorial Foundation, which is nearby.
Be prepared. That parking lot is enormous and that time of year will be packed.
See them as early as possible to avoid heat.
Then, take a trip to Baltimore Harbor. Sumter, Navy Ships, The Yards and aquarium can all be done in a day.
That way you get a two Fer...
Smithsonian Aerospace will consume at least an afternoon, as will Natural History.
Be sure to walk around the White house, stand in Lafayette Park, at least walk into the Willard, walk by the old War Mansion.
Jefferson, Lincoln, WWII and Vietnam wall are all bear each other.
Go under the Lincoln Memorial.
Go by Treasury, near white house.
Etc...
My mom’s husband’s aunt was the original director of tours at the Women’s Military Museum. We got a personal tour. very cool.