Goddamnit. Let me just throw something out there.
My dad once told me about a kid, who's parents were Amish. His parents never let him, NOR even told him about the outside world and the experiences. When he was old enough for school, his parents sent him out, and he was completely overwhelmed by the new knowledge, he didn't know how to handle it all, because there was just too much new stuff in his life, good, AND bad. As this was not an amish school, but a public one. I'll stop here.
I'm gonna take an educated guess, because many of my old friends when we were young were exposed to more 'mature' things. When I met them, I was a kid who was happy, yes. But I also was much more prone to emotional pain. When I experienced many things that were emotionally painful, or much more 'mature', I developed a thought process. "This is life, life goes on, and you gotta think happy thoughts, even when it throws a brick at you." When I experienced alot of these things, Sure, I was less enthusiastic about alot of things, and yes, I was less emotionally vulnerable. I'm not gonna force any suggestions on you, just giving you my personal experiences.
Though, should you teach your son to play DF, normal version or not. It's really YOUR choice. not ours.
Take from it what you will.