Can’t disagree that I played a factor.
Question is if one wants to avoid a CPS investigation and obtain a third-party record for the court, how can that be done?
It can’t. Anyone with credentials to whom you might go is required to report to “authorities” if they suspect child abuse. Anyone without credentials cannot be used in court other than as a character witness. Such don’t usually have any value in the courtroom.
Tell the father to get a voice activated tape recorder that the son can place in his room or in the house so when the abuse happens again, there would be a record of it.