Is it an option to not go?
Seriously. To maintain permanent 'clean' you have to change all areas of your life. At least I did. You can't control your DH's use but you don't have to go out to parties where you know the access will be abundant.
Is your DH supportive? Is he willing to stay home with you or do something without mj? If so, then missing the party shouldn't be much of a big deal.
I can tell you that removing all access and changing my friends and habits is what has helped me to stay clean.
I hope you can find something that works for you. Trust me - these seemingly little decesions add up to be a lot of big ones that keep you clean. Change is slow and takes EFFORT. It's not easy or comfortable to change your life so much.
Blessings to you this day and strength to do what is right for your recovery. You deserve it and so does your family. Your real friends would want that for you also.