Hi Ginhee,
Believe it or not I still play with my Legos, and I'm an architect!
I would steer him into the right direction with weekend field trips so he can see iconic buildings that are in the area. Depending on where you live, the best place to go would be downtown. There he can see how imagination, creativity and passion can develop into great design.
Let me know if you want some concrete (no pun intended) locales of iconic buildings!