The U.S. Naval Academy is open to the public, and you can take a 1.5-hour historical tour around the yard, which includes learning about its architecture, Academy traditions, and midshipmen life.
If you're not into nitty-gritty military history, at least go for the sailors in uniform.
The Academy also runs two hour-long, fun boot camps for kids, teaching them how to march, chant, and take orders from Naval officers. Kids also learn Navy lingo and to read nautical flags.