So, I went and made it through the visit! Having my sister there really helped cushion seeing my step-mom. I got to see my niece, too, which was fun. We didn't talk much about the past except at one point she brought up how "horrible" I was on a particular trip and I said, "I was always horrible" not realizing until later how I had put myself down.
We went to a local Ice creamery for my sons birthday so we did end up at a local spot that was a mutual meeting point where we all just talked about the day to day stuff.
I was glad to see my dad.
So, all-in-all it was a good trip!