So I guess my initial suggestion of half of an oil drum, a pile of dirt and a bunch of sticks won’t work (random, but those were my first “design” materials)….I LOVED Legos – and they are very popular with my own 11 year old, but NOT as popular as Minecraft (as several others mentioned), which is incredibly 3 dimensional and spatial. My rugrat has designed amazing forested amusement parks with water slides into underground caverns, floating forest islands, whole worlds of landscapes and structures. I don’t like it because of the blockiness, but I suspect its the future of BIM in fledgling form….but of course it only works if the kid has access to an ipad or computer – the ipad version is free, computer version is $30 or something like that.
What about a mini Japanese style rock and sand garden? I do like the graph paper and template idea too…How fun and exciting to be able to encourage a young one to design!