LMS, I too wish he had chosen rehab. Maybe he will at least go to AA meetings while in prison which could help him for when he gets out. My son did this at first only because it would look good to the parole board but now seems to be buying into it. Hopefull the same will happen for your difficult child.
As for what you are feeling: If your depression persists please see your doctor again. I understand how low a person can get when their child is making poor choices and reaping the consequences of them. Not sure I would encourage the grandkids visiting their dad either if it is only going to be a few months seperation. Although I have read that when the families maintain close ties and visitation the inmates do better overall. That said I do not visit my son. It is a very invasive patdown and scrutiny to get in much more than at airports according to husband. husband has little that phases him but he hates it. He said it is very unplesant and I just won't subject myself to that. I write occasionally and take a call here and there.