I was an oddball when it came to this. I did not enable at all, except for one time and it was done purposely (couldn't take him pacing and scoping out what he would hock next so I threw a $50 bill at him to get him to leave)
My first priority was my children. My xhb was very heavily into crack, my first rule was, you leave this house to score drugs do not come back. I was not risking having my kids taken away and all the drama anymore.
GO With your gut, you don't need proof, if he is actively using, you shouldn't have him around the kids at all period, that's not being mean, that's being a loving mother, stop worrying about his feelings and put you and your kids first. He is a grown man, and he will choose whatever road he wants to follow with or without your help.