Oh @Lordofthebutterfloofs it's such an awful situation, and so very difficult to deal with! Especially because of your beloved grandfather.
I'm here to tell you though, that I did this when my dcs were exactly the same ages as yours, and they are now in their thirties!
It's been a very difficult and painful thing in my life, yet I have to say the upsides have been completely worth it. At the beginning (where you are now) it was like a bereavement, mixed in with intense fear and anxiety, guilt, doubt... as well as a distant smidgeon of relief.
Over the years, apart from a couple of failed attempts at communication, which actually served to confirm to me that I made the right decision, there has been no contact, and the relief has increased. But the sadness that it had to be this way hasn't gone.
I did the right thing for myself. And I did the right thing for my children. I was free to be a better mother as I didn't have to devote my emotions and mental energy to 'managing' my m's abusive behaviour or keeping myself sane.
So many years later, I still suffer occasional sadness, but really I know this was the only way. Now I feel sad for her that she is so damaged that she is unable to have any satisfactory relationships with anyone. That she has missed out on a meaningful relationship with the good daughter I was, and would have continued to be, and had the capacity to be, if only she'd not felt entitled to behave so appallingly. That she has missed out on her grandchildren. That I have missed her, (while not missing her abusive behaviour) that I haven't been allowed to have a decent mother. Even now I'm sad about that.
I read a phrase on here the other day, someone saying they were going to write a book about people who take this step, calling us circuit breakers. And I thought yes, that's what I am. I'm proud to have broken that circuit, and to have decent, loving and mutually respectful relationships with my own dcs. I no longer feel shame or doubt or guilt for having done this. But I still feel sad sometimes. And that's actually ok.
It will get easier 