It's nice that he would rather you tell his Mom. I think he is avoiding responsibility for his actions.
My H did not have a good R with his Mom either and as far as I know he never did tell her (she has passed). I didn't either.
D's didn't have a close R with her (saw her maybe 5 times in their lives)and she did little to contact us. Either way, I would not have been the one to tell her.
The only member of his family I did tell was one of his brother's that was calling the house to get ahold of him. Then it was a simple "he doesn't live here anymore, you should contact him on his cell".
Your integrity will serve you well. I have always taught D's that integrity is the one thing in this would that can never be taken from you....you have to give it away.
