When I read your post, as Ann asked, I had the same question. Why do you have to tell him?
When he does receive the news, hopefully he will seek the support and guidance from his treatment facility to stay focused on his recovery, too.
When my sister was in her treatment center, there was an outside issue (having to do with court and an exbf) my mom wanted my sister to know and tried to go through her counselor. Her counselor mentioned this was another thing my mom was trying to make easier (control) and really should just let go and let my sister deal with whatever comes to her. It's very difficult to step back, but sometimes it's exactly what needs to happen.
Prayers for all those involved and affected!