My concern is not just that it would be traumatic, but that it will be so traumatic that he'll rationalize himself into a "belief in belief" situation. I had my crisis of faith when I was close to his age (14) and I wasn't ready to accept something that would alienate me from my family yet, so I simply told myself that I believed, and tried not to think about the issue. (I suspect this is why most people don't come out as atheists until after they've established separate identities from their parents and families.

A lot of people never escape from these traps. I think waiting somewhat--until he's somewhat older and more mature--will make him more likely to come to the right conclusions in the end.