Ask yourself "Do I want a POLY life or a life with these two specifically?"
If you just want a relationship with these two specific women and cant really see yourself being interested in other people, "suppression" (gods I hate that term) is more viable. Given enough time, feelings can cool down to manageable levels and you may find you didn't actually like Kim as much as you thought you did.
If you are shooting for an actual poly life, suppression is relationship suicide. Mono and poly dont mix and you will end up in a situation where you or your wife will be very unhappy and the other very happy depending on who gets their way. Eventually one will start to resent the other and it will eat your relationship alive from the inside out.
Best idea is to answer that question and go from there.
If the answer is you want THESE two women specifically and you'd be happy with just them, it MIGHT be workable. It sounds like your wife is basically (emotionally) monogamous and to someone who is mono, poly is an entirely different language so she may never understand fully. You can talk to her and determine specifically why, find out if there are any lynch pin fears holding her refusal together and if they can be addressed. But you may have to face the possibility that the concept is just not for her and she wants nothing to do with it.
If you want a poly life in general, your options are much more limited. Again, determine if she's got specific fears that you can allay but you may still have to face the fact that she's emotionally monogamous.
I am as direct as a T-Rex with 'roid rage and about as subtle. It isn't intended to cause upset, I just prefer to talk plain. There are plenty of other people here who do the nice, polite thing much better than I can. I'm what you'd call a "problem dinner guest."