I am not trying to scare you, FTL, but growing up in a home with active addiction is not really any better than dealing with divorce. I know, because like trailmix, I lived it.
Yes, they are going to be sad.
Yes, they are going to need support.
Sadness and support you can handle. Growing up feeling like you have to walk on eggshells so as not to upset someone else is insidious, and in my case, I had no idea how dysfunctional it was until I was in my thirties and had left a wake of codependent destruction in my path.
You're going to be okay. THEY'RE going to be okay. Love them, talk to them, make sure they know that none of it is their fault. They've got a strong mama to help them through.