While I'm sure you are up to your armpits in different perspectives on how to broach this rather touchy subject to your wife by now, I'm a firm believer in not making things any more complicated than they need to be.
Insofar as swinging is concerned, you are obviously aware that caution is indicated in how you bring up the subject to Ms. Rabbyt, especially since you have indicated she's a bit insecure about herself (although from the way you describe her, she sounds like a major babe...
So, the first step is to find out how she is apt to respond to this subject in general terms, as this will go a long way towards determining if you want to pursue the matter with her.
Some evening, perhaps after the two of you have shared some nice, mind-blowing cums and are engaging in a bit of after-action pillow talk, casually bring up the subject to her. But do it something like this; "Say, sweetie, I ran across the damndest thing the other day while surfing the net. It was a web site for people (say "people", not "couples"; keep it as innocuous as possible initially) who are into something called swinging".
(Obviously you can phrase this statement any way you want, with variations determined by what you figure she already knows, what she thinks you already know about subjects like this, etc. The trick is to phrase it in such a way as to indicate it's something distant, remote, having little or no effect on her. Sort of like saying "Did you know that most marriages in Japan are still "arranged" by the families?" You get the idea.)
At this point, pause a second and give her a chance to say something. Her response may range from "Swinging? What's that?" to "Swinging?!?! Ohh, yuck. Wife swappers. How disgusting!"
Naturally, if her response is something like the latter, it's best to drop it right then and forget about it, at least in the short term.
But if her response is more like the former ("What's swinging?" or the like), give her a general description of the idea, based on what you "found" on the web site. And in a sense, this is true; you just found out about this lifestyle recently, and on the net...
Either way, it will be dicey at this point, as we don't know how she might react to such a concept, so be careful. You will have to temper your responses accordingly.
If she responds positively, or at least neutral, give her some of the info you've learned, and I would emphasize how much the women are in control of the whole thing (but then, the women are always in control; else you would not be jumping through all these hoops..., and how much pleasure they get from it, etc. But even then, do not make any direct suggestions that the two of you might want to do this. Lay some of the information on her, but then casually change the subject. Give her time to think on it.
On the other hand, if she responds in a negative fashion, especially something along the lines of "What? Do you want to have sex with other women!?!", etc, start backpedaling, lie if you have to, and drop the subject. The most you can hope for is that you've planted the seed with her, and perhaps some time in the future, maybe when you all are older and she's not so insecure, you might bring it up again.
(Along about now, some self-righteous dingdong is going to get up and start bitching about me telling this guy to lie to his wife if he has to. Well, you are not the one who has to live with this man's wife, especially if she gets her panties in a major wad over this. As I have stated before in this forum, a certain amount of lying is necessary in most any relationship at one time or another just to keep the peace; the trick is to differentiate between a harmless "white" lie and a malicious one.)
Believe me, rabbyt, there is a reason most couples do not swing. Women are anthropologically hard-wired to keep under strict control not only who gets access to their pussies, but the cocks of the males they are married to or otherwise seriously involved with. This goes back to our Stone Age origins. It takes a powerful mind for a woman to override that programming and learn to enjoy the purely recreational sex one has in swinging.
Of course, once she makes that leap, she quickly discovers she still has as much control over herself and you as she did before. The only difference is that she can now enjoy the different flavors and levels of sexual pleasure one can find with different sexual playmates. The trick here will be for you to help your honey make that transition. I hope it works out well for both of you.