Tad - a number of others have weighed in on this and this is your own decision and not for any of us to make for you but I just wanted to offer you a different perspective.
Nobody is asking you to "like" anyone or even necessarily be social with them. This isn't about you. It's about your S24, his partner and the new wee baby that will be brought in to this world.
It's also about respect. Your son has asked you to be part of this celebration. He's also asked others. Some you may like, some we're certain you don't. That was HIS choice. Not your's. You have choices too. You can attend or not attend. But where I'm going with this, is that my own opinion, as tough as it may be for you, is that respect of your son and his partner and of this new life that is being brought in to this world requires you to decide if their invitation or your pride is the stronger.
I'm going to have to face this myself and am grateful that I haven't had to thus far. Not having faced it myself, its not for me to judge. I'm using your situation to think through my own thoughts about this.
It brings to mind my daughter's wedding. Her husband's parents are divorced, have been for some time and absolutely don't like each other. His father brought his partner to the wedding. When the time came for pictures, Mom, Dad, Son and his bride all stood there and smiled. And then went their separate ways. The partner sat in the back and stayed out of the way. Not all do. It's a thing.
But - I'm just asking you to think to see if you have the strength to be there and look past your own hurt to the happiness that is being offered to you.
If the answer is no, or if you think that I'm way off base, then I certainly am not one to judge.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells