Most importantly, even though the courts will only see this as a legal matter, for you it should remain a family matter as best as possible, even if it does require going to court. Even when they are at their worst, my dad told me a long time ago that "family is everything, all the rest are strangers."
My opinion would be that in your mind it needs to be one or the other and there can be no looking back. If you choose to go the legal route, you better have it square in your brain that the family element is done and gone. You'll have to if you want to be able to follow through with everything.