Threesomes is my wife's favorite ... MMF's are much easier to arrange but FFM's are awesome when you can find the right lady to do them with.
So,
MarriedBBC, you're saying your wife wishes to watch YOU perform with a white lady? Is that right?
With as many white ladies who are wanting to have the "black experience" I'd think this would be one of the easier arrangements ... the 2 of you simply go out to some clubbing, pick up a white chick after you've made out with her a while, intro her to your wife, and let her explain to her that she wants to watch the 2 of them perform ... OR, go to a swing club in your area on 'hospitality night' and meet a few ladies that way. Here's a directory ...
http://www.swinglifestyle.com/swingers/clubs/