Date people, not penises.
Dating penises is just casual sex. I'm all in favor of casual sex. In fact, penis size might be a reasonable thing to consider in a casual sex partner. After all, your goal is sex; might as well aim for what you want to fuck.
But a relationship? A romantic partner? Seriously? What kind of person dates based on "Your cock must be between X and Y centimeters long in order to go out to dinner together"? An awfully damn shallow person, if you ask me. I really can't believe that your wife would seriously use dick size as a consideration for whether or not she should have a relationship with someone. IF a bigger dick affected her enjoyment of sex with you (which I rather doubt it would), would it not be better to just not fuck the guy than to stop dating him because of his penis measurements? Would you stop dating a girl if her breasts were a centimeter too large or small? People fall in love with people, not dicks or boobs. And if all you want is a dick or a pair of boobs, at least be honest, and don't claim to have a relationship (or end a relationship) based solely on a body part.
A penis isn't a romantic partner, it's a fuckable body part. Be careful not to confuse the two.