It only happens every four years, which is forever in kid years.  I don’t think any kids younger than high school age can really remember anything about previous inaugurations. 

It is the perfect time to teach them about this extraordinary event that happens in our country every four years, the passing of power from one elected president to the other.   And in particular the historical significance of this Inauguration.

Education World has 10 great activities

This site explains the significance of the Inauguration and provides a brief history of the Inauguration.  I printed the info on this page out and read it aloud to my children

The official site detailing the events of the day

Inaugural Lesson Plans developed by that National Teachers Association

Brief Biography of Barack Obama