Long Way Gone. It would be a good way to introduce children to this topic - if you felt like it was a good idea to introduce children to this topic. Maybe children would see something on the news and ask questions? Not sure I would ever bring this book to a child unless they already knew something about the topic.
I have friends who are currently missionaries in the country Michel is from: DRC. It is still a difficult country to live in. I was surprised at the beginning of this book when he talked about how beautiful this country was. It seems like a poor and sad country full of controversy.
It is a difficult story and a harsh reality. It is told in an appropriate way for children.