okay, so I would tell your family that he is very regretful of his actions and admits freely that he does have a substance problem (i'm assuming these things are true). Also let them know that you can understand their concerns and that you are also being cautious.
That your husband has gone through rehab and is continuing counseling or treatment etc. for the long-term. (IF he isn't doing this, then he really needs to be doing this).
That you are taking things slowly and not jumping right back in, but seeing how the treatment goes and that if he continues to abuse drugs, etc. you will take the appropriate action at that point. You can email this to them or talk in person, whichever you feel they could hear you the best. Ultimately, it is your choice to stay with him or not, and they can be concerned, of course as well. Let them know you understand their concerns and in fact share them as well, and will take things slowly and cautiously. That is really all you can say to them.
Also, you may want to look into some counseling for yourself or joining a support group for spouses of substance abusers, such as Al-Anon where you will get lots of support and resources for you as well. Best wishes. Please click ACCEPT button so I'm credited for my help today. Feel free to respond here to me, even after click accept. thank you.