I take my kids here regularly and we always find something new and interesting to look at. You could spend days in here! As with all Smithsonians, buying food here is not a great idea as it will be over-priced for the quality. Your best bet for getting decent food is to get a meal from a food truck or leave the National Mall altogether. I tend to stay away from here during tourist seasons and at peak hours but if those are your only options try to take as little as possible with you inside as they search every bag before entry; you get in faster without bags. Even when crowded the museum is worth it. It has exhibits every age can enjoy.
I loved how the museum was set up. The exhibits were very detailed and I had a great time. This could easily have been an all-day event there was so much to see. When we were there there was two lines, one for people with bags and one for people without. I think there was a small cafeteria and there are three gift shops.
I hit this place upon a bicycle tour fall 2009. (Montreal - New York City). Came over here with the Vamoose bus. Of course, I have visited most of the museums. Very impressive! A must see place.
Spacious, plenty to see and touch. It's free. There's a dedicated kids area "spark lab". Several good exhibits providing snapshots of American culture. Some fun flight simulators (one-off fee of $8) in the basement near the cafeteria.
One of the most fun of the museums at The Mall because it houses Dorothy's shoes! OH yeah, there are other things, too. The American Presidency exhibit was awesome. It was cool to see all of the First Lady inaugural gowns and the china they had picked out. They also have the video camera recorder that recorded planes hitting the towers on 9/11.