Hey doogie, that's one of most awesome posts I have ever seen on T-Nation. I am dead serious. Im on my phone right now but I will type what I can here and hopefully my words make sense
First I am frankly super excited because you seem to be open minded enough that you're asking for help for getting your son reading something you don't believe in, and that both takes balls and is a sign of a really good parent. I mean, seriously.
Second I'm excited because this is an opportunity to read things that explain us--all shades from rule breaker rocker to super neat tidy hair combed polo shirted suburbia--without giving in to prevailing stereotypes in media. Se have some uncomfortable beliefs for some people to handle, but that does not mean that we are all remotely painted with the same brush (or should be at least).
I cannot recommend "Mere Christianity" enough. I read it when I was about his age maybe a year older, C.S. Lewis is a great thinker, good writer, and explains the ideas behind our beliefs. It is not a bible story book, it is a philosophy book, so it is serious...but I honestly believe if he is thinking in general about this it explains us under the hype or scandel or whatever. If he's the intellectual type maybe you could read it with him to just get a good setting and talk about it--it would help you understand your son's thinking even more by discussion and also help you to sort of get a feel for what serious Christian...as opposed to legalistic or "fundamentalists" believe.
In truth I hate the word fundamentalist because it has a serious bad connotation these days the way it has been used and abused by media and others. Fundamental beliefs are central to anything, but the word has become and epithet to describe a number of kinds of Christians people are scared of...not you, just in general. In other words too politically charged of word....anyway, I digress. In all honesty I would really suggest reading whatever your son picks up to read. Not through any desire to force you to believe something you currently don't, but out of a very fundamental hope that you can see what we are really are about and understand what we want to be without all the political baggage.
I would also really, REALLY say that it DOES NOT MATTER that your son doesn't know the "bible stories". They are interesting, informative, lessons...but they are not the "core" of the faith nor a reauirement to be accepted by people of the faith any more than knowing how to play an instrument is a requirement and prerequisite to be passionate about music and talk with those who are passionate about music. Millions of people have started not knowing them, it is fine and expected and not an issue.
Its not about what stories you can recount anyway so much as it is about where your heart and head are going. People like Alice Cooper grew up as pastor's kids, hell married a pastor's kid as well, and went through their own Odyssey. He teaches bible study now of all things! And he srill puts.on an epic show, I saw him this last year and was blown away.
People like Head and Fieldy from Korn. People that totally ignored everything having to do with Christianity and made fun of it most of their lives. They're both believers now, I'm pretty sure they didn't know the "inside.Christian" things when they started going to.church lol
Anyway, I'll think more on this and hope to give you more recommendations