Is there anyway to have the reunion at someone else's house? That way you can leave if you need to. Otherwise make a plan. Ask your sister to change "PROBABLY not drink" to "not drink" as a support for you. If none of the above is possible, then just commit that you WILL NOT DRINK. It might be eye opening for you to see what alcohol actually does to people when you can stand back and watch objectively. Good luck. Stay close to SR. Even post as it's happening (time to get a smart phone) so that you can have us "there" with you. Technology is good.