Going to DC.. your favorite things to do

I guess maybe the "one thing" might be one of the open-air (depending on the temps) bus tours so you could see all the monuments and get the obligatory photos.

You don't have time to "go to the Smithsonian" since that's made up of 19 (I think) museums. lol. I guess I'd do a bus tour of all the monuments, then go to wherever my kid wanted to go, if I only had such a short time.

The Spy Museum was GREAT. DS would have spend all day there.

I'd definitely skip the hop-on/hop-off buses. We spend most of the time in traffic. Waste of money.

The food court at the Native American Smithsonian is really good.

Since you only have a couple days, you should definitely do the monuments tour BUT I would also do one at night. The monuments are really nice at night. If you can only stop and see some of them I would recommend the Jefferson and the Lincoln. The Washington monument is really cool to walk around at night (the nice thing about them is they are open on the outside on Thanksgiving which gives you more time). The WWII monument is also really cool and is very close to the Washington Monument. That one you need to see during the day. The Jefferson and Lincoln are nice either time of day.

Skip the American history museum. After they redid it, it just doesn't work well. It is my least favorite of all of them. National Gallery of Art is cool, especially the walkway between the buildings. The museums themselves are not that interesting if you are not into fine art (I like them but I know some don't). The Air and Space is really cool but will be VERY busy that time of the year so allow for lines.

The Native American museum doesn't have a good flow to it so I wouldn't bother. It is hard to navigate. People like the restaurant inside but honestly, it is overpriced museum food.  You can do so much better.

Natural History is really nice.

Spy Museum is quick (won't take much time). I know they are moving it so check and make sure it hasn't started moving yet.

Newseum is really cool but you need a lot of time.

Holocaust museum is amazing but you need tickets and most likely won't be able to get them right now.

You won't be able to go into the Capitol and it is being worked on right now so it is covered with scaffolding.

I would pick one museum (Natural History or Air and Space) and then do the sights from the outside.

If you want a GREAT place to eat.  Go to Good Stuff Eatery.  It is behind the Capitol Building.  The owner was a winner of Chopped and the burgers and shakes are AMAZING.  We go down there just for that. 

Let me know if you have any questions.

We've lived in the area for a little over five years now, and I still love to go to the Library of Congress. Aside from the amazing architecture, there are always interesting exhibits.

We just got home from DC on Thursday!

We rented bikes (you can pick one up at stands around DC) and viewed the monuments that way. It can take 20-30 minutes to walk from monument to monument but on bikes it was faster, enjoyable, and easier. You can also ride along the water to see all of the smaller monuments - like FDR and Martil Luther King Jr. We did an enjoyable ride and it took us about 3 hrs to cover major ground. We had many tourists asking us where we got our bikes.

One evening we hired an UBER car to go see the monuments at night - we went to Lincoln and saw that one, and you could also see the Washington memorial lit up and the capital building. We also did the Vietnam and Korean monuments at night, but viewed the WWII one from the car. The car just waited for us. Cost $10. 

Our favourite museums - holocaust museum, air and space museum, natural history museum and the American history museum. We went to the news museum, which is very good if you have time but the others are far better (and the others are all free but the news museum (and spy museum) were pricey).

The air and space / natural history / American history museums were smithsonian museums. We spent about 2 hours at each, and about 3 hours at the holocaust museum. We enjoyed the capital building (the tour was a complete waste, just walk around / wait in line to go into congress) but the library of congress building was gorgeous!

If you have time for good food, we had a fantastic dinner at Ambar - Balkan food. The neighbourhood was hip and edgy (we preferred it to georgetown) and the menu was great. For $50 each we had all you can eat tapas and drinks. We also had a great meal at Zaytina - high rated Lebanese type food - book ahead, like a week ahead, and we loved Joleo - fantastic Spanish tapas, broughtme back to spain, they also have a location in Vegas.

Have fun!

National Cemetary and Tomb of the Unknown Soldier.

We spent a week there this summer and still didn't see everything we wanted to.

My favorites:
-Library of Congress. I was really surprised at how much I enjoyed this.  Excellent tour guide, beautiful architecture, interesting exhibits (and not too crowded).
-Holocaust Museum.  We had no problem getting tickets the day we were there. It took us about 3 hours to go through the entire museum.
-Arlington Cemetery
-National Portrait Gallery
-Mall/monuments - It took us most of a day just to walk around and see all the memorials (I didn't even know there was an FDR Memorial!)

I did not find the Capitol tour all that interesting. Also didn't care for the Native American Museum.  

The National Gallery of Art was cool, but I have no background in art, and I did get tired of it - I should have just hit a few highlights and not tried to see so much.

I enjoyed the Natural History, American History,and Air &Space, but they were all very, very crowded when we were there.

Just want to add --

You don't need tickets for the holocaust museum every month. Only during the height of tourist season. Right now you don't need tickets. We went last week without a ticket - they don't even give them out now. It was busy. Go by 10 and it isn't as busy. I've been to a few holocaust museums and this is known as the best.

We also did a show at the Kennedy centre and it was a wry memorable experience.

Lots of good suggestions from the peas! I will second the suggestion to eat at Jaleo (Jaleo link) - yummy and fun. As for deciding which museums to see on limited time, take a look at the websites for the Smithsonian and other museums you're considering, and then prioritize based on your own family's interests. You'll also want to check whether any of them will be having special exhibits. DS did not like the Newseum; his favorites are American History and Native American (and he also raved about their food court). OTOH, DDs both love the Natural History museum (where their brother is bored). We all like Air & Space and the Botanical Garden.

Love the FDR memorial (which is better in the daylight). Also like the Iwo Jima memorial, the Lincoln, and the Jefferson - all of which are very nice when seen at night. Kennedy Center looks cool all lit up at night as well (even if you can't get tickets for a show).

I second the Mt Vernon idea. National Harbor is also fun, but it will be crowded because of the nearby outlet mall, plus there are lots of shops and restaurants there.