Super awesome learning experience!
Just a heads up: although the site doesn't close until 5, the last Hoover Dam tour is at 3:30. I know this because we missed the last tour by 15 min. Sad face.
BUT we were able to go to the museum. Admission for he museum is $10 per person, which is fairly priced.
Walking into the museum is like going through TSA but you don't have to take your shoes off. After, you take souvenir photos. Then, you buy your tickets.
The museum is small. I believe the main museum is one floor and the 3rd floor consists of the observatory room where you can get a 360 degree view of the dam as well as the Art Deco to the left side of the dam.
I would definitely come here again someday when I have kids if my own.