When he gets older, a K-1000 or some similar camera would be good but he'll need a few more years before he can handle that much gun. For now, a 35mm point-and-shoot would be more appropriate.
A P&S digicam might be best for him to start out but I still think it important to keep film in the picture. Choice of equipment is secondary as long as he gets a well-rounded experience and good guidance.
Just let him shoot pictures. That's the most important thing. :)
Good stuff ntenny!
I have a three year old nephew who did his first cyanotype/sun prints last summer and now I've got him into large format.:D He loves the dark cloth, the upside down image, and the cable release.