So sorry for your loss. I would definately go, for 2 reasons. 1. For your own peace of mind, sort of a regrouping. 2. To honor your anniversary and memories of being there together.
I think they will absolutely give you a button. But, I would be careful about wearing it if your are feeling especially emotional, because the CMs are likely to wish you "Happy Anniversary" when they see it. It may make you smile, but they may catch you at just the right, or wrong, moment and have the opposite effect. I would just go prepared with a box of tissues and try to focus on the good memories. Good luck.