At all of the National Parks in America there is a junior ranger program for children. Each park is slightly different, and some charge a small fee. It is also tailored to the child’s age, with different levels, but it enhances the enjoyment of the places for the kids and they learn lots to.
At the canyon it is free, and they only have to complete one ranger walk and get the ranger to sign their book to get a badge and patch when they are through.
You can ask for the book at any information center. We got ours at the bookstore at the Desert View area.