Yes, you will be facing a room full of people who know, and that is very hard.
They may all be wondering why you are giving him a second chance.
They may all be thinking or saying all sorts of things. But, remember, that your husband who had the affair came from this family, and the origins of his affair come from this background, and it has a lot more to do with him and his family background than anything else, and nothing to do with you.
My wife, we used to go to family get-togethers with her family, of all the people there, and considering the various people over the years, sisters, nieces, nephews, stepfather, stepmother, father, mother, I and my wife were the only ones who had not cheated in our marriage...make that a correction, I was the only one who had not cheated, I just didn't know it till 3 years ago.
However, I also found out three years ago, that my wife was secretly smoking marijuana with one of the stepsisters, and everyone of the family knew it, and knew that I didn't know (they didn't know about her cheating though). I know now that this gossipy family, who gossiped about their affairs, their cheating, their divorces, their drug use (and a lot more than marijuana), loved the secrets, loved violating the secrets by gossiping, and loved the chaos of other people's relationships.
I also know, without question, as friendly as they were to my face and I to them, that they would have loved nothing more than to see our marriage crumble, just one more thing to gossip about, and that way my wife and I'd be in the same boat as the rest of them with their numerous relationships and divorces.
How do I know? Well, I'm not even anti marijuana, and nobody ever invited me to smoke, not once, (although I would have turned it down because of a clause in my life insurance policy which would void my insurance if something happened to me and I was using and also because of my license, which can be restricted it I'm found to be using)...just my wife. I knew that the sisters used, they knew that my wife did, but secrets and gossip were the order of the day.
So watch that family carefully, and think about the fact that you lived in the same town, with an affair that went on for 3 years, and your recent DDay, you probably don't know the beginning of it.