I would not come up with an "excuse" for not going, that would just feed the fire. I would find something else I wanted to do more, would stop by with/when hubby goes over and give a card to the birthday boy and then explain I had another engagement and leave and go do something else I would rather do. If you can have a girlfriend come at about that time to pick you up, that would put icing on the you-mean-people-and-your-parties-are-not-who/where I-want-to be/with