There's a great site for kids of all ages and their parents to learn about the U.S. Government - about citizenship, how laws are made, and much more - and it's divided into age-appropriate content areas... It's called Ben's Guide to U.S. Government for Kids - and your host is Ben Franklin.
This makes a great family learning activity!
You can find it here:
http://bensguide.gpo.gov/index.html