Good on ya paul! Tell him Otony says he did a GREAT JOB! Encourage him to build all you can, it is great for creativity, eye-hand coordination, plus it is just plain fun.
My boy and I enjoy Legos quite a bit. He is just 4, so we are still using the larger sizes, but I still have my old Legos to give him when he gets older. I'm really looking forward to that.