The Young Peacemaker has been recommended to us by several other families. We just finished going through it as a family and most of us benefited from it. Many of the ideas in the book are probably too much for a child under 7 to grasp, but all of the children learned from the stories and some of the principles. We bought the kit that comes along with the book which contains worksheets and activity pages for each chapter. These are definitely for those who can write and read with good comprehension.
Overall, this is a great resource for a family to use and re-use. We plan to re-read it again next year.