Kids love to take stuff apart and put it back together again. Educo's Master CarpenterWorkbench would make an awesome green gift for your budding engineer. It's completely non-toxic and old-school adorable. Both high quality and good looking, there's no plastic, it's all wood, and even comes with extras like a tool belt.
I think this would make for something dramatic that Santa Claus might leave by the tree. It comes in a box unassembled and is easy to put together. There are a lot of plastic tool sets out there, but this is worlds apart. My four year old son thinks it's the bees knees. Wood feels good in your hands and there's no scary chemicals to worry about that can harm your children. Good for us, good for the earth and guaranteed to keep them busy while you get dinner ready. You can find it HERE.