For his birthday, we (myself and Brother-in-Law (or BIL)) took Son and Cousin to (cue James Bond theme) the International Spy Museum in Washington, DC. It was enjoyed, in decreasing order, by myself, BIL, Son and Cousin.
First, the good stuff. The museum was very nicely put together, if a tiny bit crowded. They do suggest getting advanced tickets, although that adds to the price. The exhibits run through pretty much all of history, and all of spydom, from B.C. and biblical references to Cold War and current affairs, and from code cracking to assasination to transfer of secrets to wiretapping and bugging. In most cases, they had examples of the hardware they were describing, and several short films (5-10 minutes) were playing constantly. They even had an air duct you could crawl through and spy on the folks below, which Son and Cousin loved. And the gift shop, while expectedly overpriced, was a lot of fun, too. The Spy Cafe, next door, was where we ate lunch, and that was decent as well. The whole thing took about 2.5 hours to go through.
Now the "bad" stuff. It was a lot of reading, which Son, just turned 9, tolerated, but Cousin, age 8.5, had no patience for. As a result, they were moving through things much faster than I was. BIL wound up following them, and they got to the gift shop awhile before I did. Wife mentioned later that the website does suggest ages 11 and up, so we were taking that chance. Also, we got to DC around noon, and found no street parking, and almost no open parking garages. We finally parked about 5 blocks away, (at G & 13th streets, in case you're interested; the museum is at F and 9th), and walked it. So nothing really bad, but just stuff to be aware of.
I've wanted to take the family to DC for a number of years, to see all the sights, but this continues to make me want to wait a few more, until the kids are older and better able to appreciate it all. (But I sure had fun...)