As far as your S is concerned, I asked the pshcyiatrist teh same question. He said that the fact that my kids are close with my family (as I beleive yours are as well) is very good. He said that they will feel the stability and sense of family with the extended family.
Also, I believe that if you can be emotinoally available, strong, reliable, etc... that will be another thing in your favor.
I would also recommend counseling. I think a lot of these problems come about becuase these guys (or gals) keep stuff bottled up for years. If your S can learn to talk about what he's feeling, that will be good.
With all those things in place, he will be just fine... better... he will learn from the mistakes he's witnessed and lived through and he will come out of this an amazing person (which I'm sure he already is).
Although we don't get married and have kids only to end up divorced, sometimes it just has to happen. And I think there are many things we can do as parents that can keep our kids as minimally impacted as possible.
You're an amazing mother. It's clear to all of us here. That will be instilled in your kids their whole lives. They aer so lucky to have you.
