Okay, let's finish up with D.C. here.
Our favorite place that had quick delicious sandwiches was The Potbelly Sandwich Shop. They had these delis in Chicago as well. We loved this place because the prices were reasonable, the menu had something that everyone liked, and their secret relish was truly one-of-a-kind and so good!! The place is packed during lunch hours.So, unless you don't mind waiting in line or having your kids keep tugging at you and telling you how hungry they are, my suggestions are to arrive earlier or later than the lunch rush. Also, the thing to remember about the Capitol area, everything closes when the typical work day is done. Things close up around 6pm and almost everything is closed on Sundays. Be prepared because we weren't and ended up taking the Metro a few stops away to get food.
Speaking of the Metro....it's really a great way to travel around D.C. There is no need to rent a car. We were able to get around all over D.C. Unlike NYC, where the subway only goes uptown and downtown, the Metro will get you just about anywhere. Some of our favorite stops were Chinatown/Gallery. This area had the International Spy Museum, National Portrait Gallery, restaurants galore, and a great movie theater. People asked us why a movie theater on vacation? Well, when it's below freezing outside and you want to get out of the hotel, the next best thing was the movie theater where we saw Alvin and Chipmunks, The Squeakel.
The Spy Museum was really a great place to visit. Our kids really enjoyed it and had a great time. The admission is a bit pricey, but well worth it. Also, all the Smithsonian Museums are free so one can't complain too much about paying for admission to one museum. You get to learn about espionage and even get to be one. Be aware of the common tourist trap...........the Spy Museum Store. You have to walk through it to exit the museum. We did get caught up in it and I think we did because we all enjoyed it so much and the store had some great shirts and souvenirs.
On another day, we went to the National Portrait Gallery. My husband and I enjoyed it; however, I think kids younger than 5 y.o. will have a tough time. There are lot of paintings and statues. They are beautiful and interesting, but after 3 floors of it, my 5 y.o. was having a hard time slowly getting through it all. My husband is a history buff and so he entertained the kids with historical "stories" to keep their attention. Again, it can be tough for the little ones. I would suggest making it to the Presidential Portraits first since my 8 yo was studying the presidents at school and these paintings were larger than life.
Having mentioned that the Smithsonian Museums are all free, the National Mall is surrounded by these free museums that take days to get through. We were amazed how some people thought they could get to everything in 3 days. Our suggestion is to not try to do that. It just becomes one big discombobulated mess. If you're there for 3 days, then pick 3 museums max., especially when you have children. I would suggest The National Air & Space Museum; The Museum of Natural History (you can spend 2 full days here); The Museum of American History.
The Air and Space Museum is place of wonder for the kids. They have large airplanes hanging from the ceiling, rocket ships on display, things children can touch and play around with. We spent almost 3 hours there before we headed off to lunch and then came back to finish the rest of it. The lunch area is convenient and pricey. Again, if you're on a budget, pack a lunch and you can take that to the eating area and relax for a bit before finishing up the rest of the museum.
The Museum of Natural History is another great place for the family. There are many exhibits and many floors. If you get a chance to see an IMAX movie there, I would suggest it. The kids loved the dinosaurs IMAX movie and then had a chance to follow up with the displays about dinosaurs. My boys enjoyed the mineral exhibit. The Hope Diamond is there and they were fascinated by it. There was the astrology area where the kids had a lot of hands-on activities. In the basement is where the cafeteria is located. Also, the museum stores are down there as well. I found this cafeteria to be quite good and the prices were reasonable for the food that was cooked fresh for you.
The Museum of American History had the longest line to get in. It moved fairly quickly, but beware there might be a long line for the entry. In the basement area is where my kids loved playing in. They have the Sparks Invention Lab here where they hand out free pins with the logo and you can go in and invent things from their kits. My kids made an electrical circuit to get a fan to start and float a ball. They also had the opportunity to build things that made music. They have supervision there where these "scientists/inventors" would guide the children with their projects. I think my kids could have stayed in there all day. They do close earlier than the museum so time things out. You don't want to arrive there at 3:30pm and just as your child is really getting into his/her invention, they have to leave because of closing time (4pm when we were there). The other floors had a lot to see as well. Remember there are a lot of people and a lot of exhibits so keep your kids nearby as they are anxious to see everything and one little peak of curiosity could lead to lost children. We saw quite a few of them there.

If you haven't seen or heard about Groupon, then this is something you must visit. This site offers coupons to major cities. What I love about them is that they offer you the discount (typically 50% off) and if the total number of people needed to purchase the "groupon" is not met, then they don't charge you for it. If it does exceed the total of required purchases, then you receive the coupon. So, I purchased a groupon for a restaurant in Dupont Circle (another nice area for restaurants and shopping...our fav: Trader Joe's). This restaurant is called Mezza Luna. It's a Mediterranean cuisine with a variety of tapas. These tapas were large enough to share. We ordered several and shared them "family-style". Their food was delicious and they were very accommodating with our children in regards to making their dishes less "fancy". This translates to "please no green onions on the top", "no nuts. our children are allergic to them", "plain pasta with butter". They were really wonderful with all our needs.
We did hit the Memorial Parks. The kids enjoyed the walk (again, if you have little ones, take your stroller) and seeing all the historical monuments. We walked a few miles and it was a lot of fun; however, you can take the Metro to these areas if your legs are getting tired.

One place I don't want to forget to mention is the United States Botanic Garden. This place is a gem! The plants and gardens are gorgeous and our kids really liked visiting this place. There were so many exhibits to visit. One wouldn't know it by looking at it from the outside. I wouldn't miss this place. It's a great place for the kids to run around.
Finally, we did purchase tickets to see the Terra Cotta Warriors at The National Geographic Museum. It was an okay exhibit, but I am comparing this exhibit to the one I saw at The DeYoung Museum in San Francisco many years ago. This exhibit in D.C. was smaller and the kids enjoyed it. The garden/courtyard area is definitely a photo op location. I was very impressed with the photography as I'm sure most people are. The photographs are truly spectacular!
I almost forgot to tell you about the Kennedy Center. It is quite the site at night. I guess I almost forgot this place because it was someplace my husband went to every night for work. We didn't see a show there since we have already seen the show, but if you get a chance to see something there, we think you would enjoy it. It's not always easy since not all shows are appropriate for children, but I did want to mention this for those of you who might have a babysitter/relative on hand to watch the kids.
All right my travelling peeps, go take your kids out! We are hoping this history class just expands their experiential background for their own education.