We don't plan to eat near the hotels - we plan to eat around (in)the Smithsonian - all we want to do is sleep & stay gone most of the day - til the Smithsonian closes @ 9ish..
Smithsonian Museums close at 5:30, with a few of the more popular open until 7:30 in the summer (Air and Space, Natural History, American History that I know of). There will still be a few people milling around the mall in the evening before it gets dark, mostly concentrated around the monuments. But generally after 5 most of the populace moves towards the restaurant corridors just off the mall area like Penn Quarter.
Using the bus from Dulles to go into town would be a huge pia and take a big chunk of time and $. Honestly I'd spend the money to stay in Alexandria at one of the options recommend around the King Street station. Easy in and out to DC, nice area to wander around in the evenings and still feel like you're in the city, and good food options. Tysons is incredibly congested and very very car oriented. While there are food options, they're very difficult to get to on foot. You're talking about crossing 8+ lanes of traffic that carry a tremendous number of cars and commuters, and it's not at all pedestrian friendly.


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