Seriously dysfunctional family... do I cut them out?

This is hard to sum up... I grew up with a mom who was bipolar and never taking her meds appropriately. Her emotions controlled the house and even caused some very serious issues between me and my younger sister (my only sibling). My mom became an alcoholic 8 years ago, began having an open affair, my dad divorced her 3 years ago and she is now engaged and living with the "other man". My sister is very overprotective of my mom (still falling into her victim bs due to the alcoholism). My sister is still "co-dependent" thinking she can save her and when I speak with my sister, we just do not discuss my mom at all. I am tired of the middle of the night phone calls while she is drunk telling me she hates me and wishes I were never born... I guess I have always been the black sheep because I never gave in to my mother's crap and my sister is the golden child because she always did and still does. My sister came for a visit and physically attacked me in my home (with all of our children present). She has done this before to me and my mother during visits with her. She is 31 years old and my dad is making excuses for her behavior (she is under stress due to selling her house and moving and the baby not sleeping well). Her 2 sons were completely calm (still playing with their toys like it did not phase while she was on this rampage screaming and beating the crap out of me- like they are numb to it) while my 4 children were hysterical and terrified. I have tried to have a normal relationship with her for the sake of the kids but I can't let this happen in my home or around them again (this happened years ago when my oldest was young and she attacked me with him in my arms). If I cut her out, I will have to cut out my parents too... my mom only calls when she is drunk anyway (so that is a no brainer) but my dad will continue to keep my mom and sis up to date on my life if I continue to keep contact with him. I let my oldest son go visit him for a week this july and he promised my son would not go to my mom's house... he sent him anyway and lied to me and told my son to lie to me and my son was put in the middle of a physical argument with her and her fiance who both were drunk- my son called my dad to pick him up and my dad told him to hang tight until the morning and not to call me. My dad doesn't think he did anything wrong by lying to me and telling my son to lie to me and leaving him there or sending him there in the first place. Should I cut them out? No matter what, I love them because they are my family but they are hurting me and I have worked very hard for my children to have the normal life I never got to grow up in....but my family is just tainting that. My husband thinks I need to just let them go... it just hurts so much!