Adding my prayers for your situation. I've been in your shoes with a family member and its so very hard to remain optimistic when you see the sewer they are living in. Raise your eyes to the Lord and know that He will lead the way. Your son and his children will get through this easier because you care so much. Just stay supportive to them and give their mother to God. The behavior of all grandparents and parents involved with an addicted mother or father is the best example those children can ever see. If I can offer you one solid piece of advice, it would be to let those children hear you praying for their mother. They know there is a problem, their gonna love her regardless, and it helps them to know that your not turning your back on her during a bad time. Even if they have to stay away from her, hearing your prayers on her behalf really does help to allay the resentment that the children will feel to those that are keeping them separated from her. May God bless your family and bring you peace.
Cherylk