Katie, I don't have the answers but I feel your pain and children have always been very special in my heart.
I also admire that you are looking out for what will be best for these children. How blessed they are to have you in their lives.
My thoughts on your situation are to maybe see a lawyer first and find out what your legal options may be. I'm not sure if you already have legal custody of these children, but that may be the first step if not already in place.
I will keep them (and you) in my prayers, that whatever is best is what will unfold.
Hugs