For a tough easy to build plane that will withstand a lot of abuse if flown over grass consider the Flite Streak Trainer. It uses a solid balsa ( plank ) wing, that is much tougher than a built up wing. A solid balsa profile fuse with hardwood engine bearers and ply doublers make a sturdy set-up. An O.S. LA .15 will work for basic flight, a .20 or .25 will really haul it around.
It won't do much in the way of stunts, but will get him through take-off / landing, flying level, climbs and dives and with a good engine you can probably get in a loop or two. I had one that gave a bunch of people their first successful flights and survived many a 1 point landing into the dirt.
You can put a simple finish on it with a couple coats of spray can auto primer sanded smooth and Rust-o-Leum spray paint for color.
Here is the link to Brodaks catalog for pics and details.
http://www.brodak.com/shop_productdetail.php?ProductID=2559