I think all this falls under the category of "Be careful what you wish for." This seems very erotic to you right now and others on this thread are congratulating you, I just think that the reality of her giving birth to a mixed race baby is going to cause all kinds of problems for the two of you. These same people that are cheering you on would never consider going through with this in their own lives.
I come to this from being in the same situation as you. Last year my wife got pregnant and when the doctor told her that the estimated date of conception fell within a few weeks of her participating in an all black gangbang. When I found this out, I visualized us with a mixed race baby (her blonde and me a redhead so it would be VERY obvious) and the implications for our personal and professional lives. She was raised in the deep south with racist relatives. This is just her family and does not consider my family and our professional colleagues.
We went into this with our eyes open to the fact that when a wife has sex with anyone other than her husband, she risks pregnancy. This is no matter whether or not birth control is used because even the best birth control is not 100% effective. When Amie has had sex with her black lovers condoms are almost never used because she just loves sex without them and in just about every case of vaginal sex they have cum inside her. I think a big part of the excitement for both of us is the potential risk though neither of us actually wanted her to get pregnant from her black lovers. She uses the pill for birth control and has been on it in the vast majority of times except last year when she went off the pill so we could have a baby. It was during this time that she had totally unprotected sex, all bare with 3 black men. This led to months of anxiety and lost sleep, the potential consequences of her playing with black men were suddenly very real. We wouldn't even know which of them was the actual ******* which would increase the humiliation. As it turned out our baby arrived with red hair on his his head!