This is a nice fantasy, which could be dangerous translated into real life. OK, the natural next step, then, might be to develop it into a story and post it on the site. Your wife could describe her dance night outing and the feelings of being fondled by a stranger.
Then you could write the next chapter, describing how she comes home and tells you how her pussy's all wet because a stranger was trying to get into her knickers - that chapter ends up with you fucking her brains out, of course...
Next morning, one of you suggests inviting the stranger home...

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Erotically yours... Gus