I've decided I will not be around her family with her present even if she invites me to come along. What does everybody think about me still interacting with them at all?
Take the kids to see their great-grandmother, and their other grandparents. I don't encourage LBH's to attend family gatherings when the WW will be there. It is her family, after all, and although they love you......it may cause some discomfort or awkwardness for her parents if both of you are there at the same time. I see this as you respecting them, to see them when she's not there. Those are just my thoughts about it, and speaking from experience of being the in-laws/grandparents in a similar situation.
Just understand that it won't score you any points with your WW. In fact, she'll likely resent it. But as long as you do not have ulterior motives.......which is kind of hard not to have when you visiting her parents.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!