I wouldn’t worry about your son meeting OW prematurely. I get why it would bother you but he’s three years old. He’s not going to be thinking about big picture stuff. She’ll just be a lady he met. My XH introduced our kids to a few women when we were still married and l was unaware of his activities. They would have been between the ages of five and nine. He told them they were friends and they didn’t think much of it. It wasn’t until he left to live with the last one that they started putting two and two together. If he mentions to you that he met her, you just need to keep your game face on and seem unconcerned… “oh…you met a friend of daddy’s. That’s nice.” No need to make it more than that. If it seems like a non issue to you, it will be a non issue for him. That’s the kindest thing you can do for him at this age. I know it sux but it is what it is. And…yes…you are married to a moron. (((HUGS)))