Trip to Our Nations's Capital

We will be heading to Washington DC this weekend to visit family and see the sights. Uncle L, TTG's brother, and Aunt A live in DC. We see them usually when they come to KY and we visited with them two years ago. Their house is in a great location and makes it really easy to hop on the Metro and visit all the museums and other attractions.
While there we have a few things we definitely want to see. They are:
The Smithsonian National Museum of Natural History
The National Air and Space Museum
The Steven F. Udvar-Hazy Center
The National Zoological Park
Maybe Arlington National Cemetery to leave some flowers at my Aunt Viola's grave.

We also want to spend time visiting with family. We don't get to see Uncle L and Aunt A as often as we like so this will be a nice visit.
Also, my very first friend in the whole world lives in the DC area and I can't wait to see her and her husband. We met on the very first day of kindergarten and were friends from that moment on. Even after I moved to KY from PA we still managed to keep in touch and see each other through the years.
We will be leaving on Friday afternoon and will return to KY on Wednesday.
I have about a million things to do before we leave and I don't even know where to start.
I am starting a list of stuff I need to pack, just to help me remember

1. clothes for both kids-spring and winter
1. pants
2. shorts
3. shirts-long and short
4. socks
5. underwear
6. t-shirts
   
2. pj's for both kids
3. sleeping bags for both kids
4. tooth brushes for both kids
5. plastic cups with lids
   
6. bath soap for kids
7. sunscreen (I am hopeful, although the weather prediction is rain)
8. raincoats for all
9. umbrellas
10. books for kids to read before bed
11. portable dvd player
12. dvds
13. snacks for car ride (have to buy)
14. camera
15. battery charger
16. clothes for the adults
17. all of our pillows
18. booster seats for kitchen chairs
19. umbrella stroller
20. hats for kids
21. activities for car ride
22. gum

I will add more as I think of things.

I know I am forgetting tons of things.
Help me out, what am I forgetting?
What am I leaving off the list of things to see in DC? Remember, I have a 5 year old and a 3 year old who would not behave/enjoy a portrait gallery or anything like that.