Hello Fluffy,
Our fears of what other people think, drives our actions more than we would admit too.
It limits our ability to talk with others because we do not want to offend them if we mention any "God Talk."
I find the best opening line if we want to talk to people about God is to ask people this question, "How is your relationship with the God that you are presently worshipping right at this very moment?" It is an open question that allows them to respond without actually asking them, "ARE YOU A CHRISTIAN?" That may be offensive, but when we allow them to chose any god that they worship in their response allows the ice to be broken and a conversation to be started with them. The question also allow them to ask you about your relationship with the God that you do worship and gives you the opportunity to talk about our relationship with Jesus/God.
Oh well, sounds like your son is not as reserved as you are.
Shalom