The only difference between fiction and nonfiction is trust. 

I don't have kids, so I can't say what would work. But for me, questioning the history I was taught was first the result of extreme cynicism after learning just a little bit about how things actually work. If I were to teach someone from scratch, I'd focus on building habits of questioning and making sure what you're hearing makes sense before you accept it, and even then, holding what you believe lightly enough that new information can adjust your views when needed.

Belief in good religion is a great foundation.