This all took you completely off guard. You had "confessed" your fantasy to your wife only a couple of weeks ago, and had not meant for her to tell your secret to anyone else, and you definitely were uncomfortable with the idea that she had decided to turn it into reality. However, it was also rather obviously too late to do anything about the situation now, especially because it was obvious that this was something that your wife really wanted to do.
"And hun" she continued, just as you were about to go let him in. "It would be helpful if you could tell him that your are really grateful that he's so willing to help us make you a cuckold. You WILL tell him that, won't you?"
Your wife said that as if you had a real choice in the matter, but you knew you didn't, so you then did exactly as she had asked you to do -- and in some ways, by saying that it made the rest of the evening less awkward, and made your wife and her ex feel more comfortable sitting together at dinner and sitting next to each other on the couch -- being very affectionate with each -- while the three of you watched some TV after dinner -- with you sitting in a chair by yourself. And then, later in the evening, the two of them said good night and walked together upstairs to go to the bedroom, while you retreated to the guest room.
A creampie from her lover, and you know she’s going to love it 😉