Read post #5.
How to report the change of address is up to those involved. It may be that there is no desire to get the mother in trouble.
Reporting it as being in error won’t be getting anybody in trouble. It does allow the postal service to cancel the change of address though. Without cancelling it the op will continue to get fils mail until the change of address expires.
Your post 5 simply said to take the mail to the post office. I acknowledged that somebody said to take it to the post office but nothing else I suggested.
And of course: the path of action of any person is up to them. I simply provided what I believe to be prudent suggestions.
Why you would say that to me when you too offered advice is beyond me.