I want to make sure you are aware of a book, When The Lights Go Out, especially with what is now in the news daily about terrorist threats. This is an adventure / mystery for readers 8 - 13 with a terrorist plot.
In the story, the father of the main character is able to tell his kids why he joined the army instead of going into business. He says, "After what happened on 9/11, somebody had to help keep the country safe." This opens a short discussion with his two children in which he briefly recounts the events of that day.
I found, while speaking in schools, that many children today know little or nothing about 9/11 or why it's important to them. When The Lights Go Out will help teachers, librarians, grandparents, and parents with this issue.