It’s critical that you share your fantasy with your wife. Taking her out and hoping black guys hit on her is likely to go no where, even if they were, amazingly, to hit on your wife with her husband there (highly unlikely), she will have no clue that it would be appropriate for her to welcome the attention. So you need to decide if this is something you really want. If it is, there are no circumstances that you face that other husbands haven’t faced and overcome. But it comes down to your commitment and seriousness to make this happen.
Sharing your fantasy is so essential. It tells you exactly where things stand. Maybe she finds the idea exciting/intriguing, and then you have a definite shot. Maybe she is accepting of your fantasy (doesn’t judge you for it) but tells you it’s likely not going to happen in real life but may be open to fantasy play (this was where my wife was at when I told her), or maybe she is completely opposed, hates the idea and won’t even agree to fantasy play. Whichever it is at least you then know.
Forgot to ask if she like, is ok with, or really dislikes/hates porn? Maybe she’s never watched any. Seed planting will really start by sharing your fantasy because right now it isn’t even on her radar. Once you share your fantasy toys and porn that align with your fantasy are definitely in play.