I would try to give him a Panzerkampfwagon IV with the short barrel. Tamiya makes that kit-it's the one with the crewmembers that come out of the open hatches and it's molded in dark grey. I built it and it's fairly easy with rubber-band treads. It has a lot of wheels, but overall it's pretty simple. Look at the link.
http://www.tamiyausa.com/product/plastic/135militaryminiatureseries/35096.html