Came across a link that I thought you might like to share with your kids, It’s called Ben’s Guide to the US Government for Kids, you can pick whichever grade level your child is at.
https://bensguide.gpo.gov/
Your Neighborhood and Beyond | Our Nation | Historical Documents | Branches of Government
How Laws Are Made | National versus State Government | Election Process | Citizenship
Symbols of U.S. Government | Games and Activities | Glossary | U.S. Government Web Sites for Kids