It sounds like you're willing to be the scapegoat if it means being able to play "happy family". But let me ask you: what are you really getting in return? Are they really going to drop the hostility and be civil with you? Are they willing to own up to what they did? Will they let bygones be bygones and work towards a relationship with you and your children? Or will take you as acknowledging your part as you owning up to everything that went wrong? How are they going to act towards your children?

Depending on how tangled they are with your parents, I would say reaching out to them might not be a bad idea. However, I also wouldn't expect everything to come up roses.

As far as feeling isolated, have you looked into groups that are specifically for parents that have children with special needs. I know in my city there are a couple. They arrange activities so that parents have a chance to get out of the house meet others who are facing similar challenges. It might be a way for you to build a support system and to break the isolation.