My 7 yo loves engineering, so I have been setting him challenges. (Build a bridge that will hold such and such, lift an apple without touching it, etc) Would anyone be interested in a page of ideas like this? I'm gonna run out soon.
Famous buildings and where they are in the world to teach him geography maybe? So for example you could ask him to build a famous building or monument and then ask him some questions about it like what country it is in what sort of time it was built.