Everyone is different. It depends on your wife.
I told my wife the fantasy, and she fulfilled it a couple months later, on my birthday. She told me while we were at a restaurant for dinner. She was anxious about what my reaction would be. All I asked her was if she enjoyed herself. She said yes but would not look at me when she said it. I told her good and dropped the subject. A few days later I told her I was ok if she was with him again, I just asked that she let me know after the fact. The following night we had sex, and the following day when I came home from work she told me she had been with him again. We talked much later and she told me if I would have pushed her with questions, it would have turned her off, initially. She was feeling guilty and her emotions were all over the place because she liked the sex so much with him (not her husband). I never pushed her and it was not long before he was with her twice a week and she added boyfriends.
Everyone is different, you should know your wife and how she will react to being pushed or going a little slower.