I kinda think that you cant fix this for your children. And as parents, that is instinctively (unless you are MLC and/or broken) what we want to do. It makes us crazy that we cant.
Have no expectations where your wife is involved. Trust me, your D14 will know if you forced her mother to be in her life. That would not be good for her either.
As for your son, watch him closely. Sons tend to keep things inside and find it hard to tell their feelings.
It really is your xw's choice the kind of relationship she has with her kids.
I know you get the fallout from her choice. So, you need to let those children know that you are not going anywhere, that you are there for them and love them. You can explain to them that mommy is going through something and though she loves them very much, she needs to figure out some stuff. Or however you want to explain it.
Then, continue on. Getting dragged back into the drama will not serve you well and therefore, will not serve your children well, either.
M, keep them talking to someone. Talk to their teachers and let them know what is going on. Find a female relative or friend who could maybe be in their lives.
