Cuckless Pretender May get lucky with 23 yo girlfriend who wants BBC

I am a 34 yo male who has fantasized about cuckolding since I was in my early 20s. I have never really had a problem getting girls but all of them have been very loyal. The current girl friend I have is different. She admitted to me that her fantasy is to have a threesome with two guys. She also keeps bringing up how attracted she is to black men. The darker the better. I told her I have a voyeur fetish and would like to see her fuck another guy. Really I would prefer having her tell me in detail about another guy she fucked without me there. She is really hot (blonde, tight body, nice face) but is really shy. Any ideas from girlfriends/wives who have strayed from fidelity. I would like to make this happen but don't exactly know how.