John Walsh in Antigonish, NS makes a child's size chanter for $72 CDN. http://www.johnwalshbagpipes.com/ This is a good option for young learners. A couple of my students used these chanters when they were younger/smaller. They have since moved onto full-length chanters.

Make sure you get him to a teacher. If a child that age can participate in an organised sport, they can take and absorb music lessons.