You are again implicating I am sympathizing with criminals.
here is the definition online (not the best source but you asked for a reference)
[pedophilia n. an obsession with children as sex objects. Overt acts, including taking sexual explicit photographs, molesting children, and exposing one's genitalia to children are all crimes. The problem with these crimes is that pedophilia is also treated as a mental illness, and the pedophile is often released only to repeat the crimes or escalate the activity to the level of murder. (See: molestation, rape, pornography) ]
Unless the OP's son physically took sexually explicit photographs of minors himself, molested a child, enticed a child, exposed his genitals to a child, he is not legally a pedophile.
I would define him as a pedophile in progress. Counselling and monitoring would increase the chances of him not becoming one.