I feel for you, this must be a really hard time.I hope you can get some face to face support for yourself. I work fulltime, am a single parent, but thankfully don't have to deal with the other stuff you have on your plate too. Just remember to congratulate yourself on holding it all together; you are doing a great job under very difficult circumstances.
Other than that, try and keep in mind that you cannot influence her actions or reactions, or those of your/her extended family. If legal steps are in the best interests of you and your children, take them. Her family may about face and refuse to testify no matter what you do, she may or may not embrace sobriety no matter what you do.
Its a hard habit to get into, but once I stopped factoring other people's possible reactions into my decision making process then making decisions got much simpler - it's uncomfortable but very freeing.