I'm also in California, also white and married to a vanilla Korean princess (40 y.o.), also ok-endowed (7 inches), and also dying to see her with another man. It hasn't happened and won't happen for the foreseeable future, but I am pretty sure she knows and partly shares my fantasy. We might do it one day.
Here's my advice: forget about reality for now--focus on establishing this as a fantasy that is fully shared and enjoyed with her. One night I started it by doing a light roleplay. I told her, "now I'm imagining that I am a younger man... my name is 'Johnny', and you have been dating me on the side for a couple of weeks. And tonight, you have decided that it's going to happen...". These were my words, pretty much, and well: I was lucky. I could sense the excitement rising in her like a rush of blood, and her pussy suddenly got wet in the most unmistakable way. Since then (a couple of years ago) we have turned several hotwife fantasies into a staple of our sex. I cannot stress this enough: some of us are not made to straightaway rush into the reality of our wives' fucking other men. For some of us the fantasy is very powerful anyway, it is safer, and it is delightful when fully and naughtily shared with her.
Going this slow and cautious route, by the way, something nice has happened: both she and I have become much less nervous about these fantasies. You see, early on I was terrified at the possibility that she might destroy my dream, perhaps vowing that it will never happen, or wondering aloud if I am sick, and so on. I was thus a bit paralized in my enjoyment of the fantasy, very protective of it, and always on alert. Now, however, we are both very comfortable with our roleplay, and we both draw a lot of erotic fuel from it. This is what gives me confidence that, sooner or later, I may go ahead and drop the idea of her really trying another man. At that point, even if she should say 'no', the idea will not appear pathological or outlandish to her. She will certainly be open to talking about it, and there will be room for persuasion and negotiation.
Of course I was lucky, as she did respond well to the fantasy in the first place. Perhaps the most important thing is finding common erotic ground, if you know what I mean, and then together you can move on from there. I owe a lot to these hotwife fantasies, as they have allowed me (us) to re-ignite a sex life that was really lagging too much. They allowed me to re-eroticize my wife, more powerfully even than when I first met her 12 years ago, and they allow me to fuck her like I am some 25 y.o. stud named 'Johnny'
Congratulations on your very hot wife by the way (those nipples and that shaved pussy...), and good luck in getting a hotwife.