Hi. I work for the Smithsonian (though, to be clear, I'm not writing in an official capacity!)

A lot of it depends on what you want to get out of the experience, and what you enjoy from museums. Is it possible to see every single thing? Of course not. But it's absolutely possible to have a magnificent time.

Generally speaking, when most people think about the Smithsonian museums, they're thinking of the "Big Three" -- Natural History, Air and Space, and American History. But there are a lot of other museums that offer really great experiences which might be even better for you. I personally love both the African American History and Culture museum and the American Indian museum, as well as the Portrait Gallery and the Asian Art museum. The National Gallery of Art isn't part of the Smithsonian (though most people don't know that), but it's on a lot of folks' lists (though I personally am less fond of it).

Obviously my first question to you is what sorts of things you're interested in, what you enjoy doing or seeing. The Smithsonians cover most topics under the sun, so if you name a hobby or an interest, I can point you towards specific exhibits and galleries.

I would also encourage you to vary up your experiences. Plan for half a day in a big noisy museum, the other half in a calmer gallery. Take breaks. Museum-fatigue and museum-burnout is very real, and we see it all the time in people trying to gorge the whole thing in one sitting. Don't feel pressured to see everything and do everything, because that's the easiest way for you to get in your head and not actually enjoy the things in front of you.

So yeah, let me know what you think and I'm happy to offer more curated recommendations.