If it were me, I would stay with my parents the first three nights. I have worked with bipolar people who are unpredictable (not saying that bipolar people cannot control their impulses) so I can appreciate what you feel. Not to throw a wrench into your plans, but if sister gets out of hand, that's on her, not you. But I guess we all have to deal with reality. My vote is to stay with parents, but put up with no nonsense and have a backup plan, and then when hubby comes, stay at BW as planned. Good Luck OP, I really do feel for you.
Editing to say that I have seen families in this situation to be the most understanding and loving people I have ever met.