As to the thread topic; this is something that many of us have experiences so you are going to get a range of viewpoints although at the end of the day, only you both as a couple can make this type of decision. It should be made together as a couple and understand that there can be consequences on one side of the coin along with a greater feeling of freedom on the flip side of that same coin.
While you both would like for her to have someone to openly share the lifestyle with, it is critical to be very careful when opening up about your lifestyle choices as a couple. I would agree that it can be much more enjoyable when your lifestyle choices do not have to be hidden from those you both consider friends although sharing with the wrong friends can also impact your current friendships as you know them.
In my time within the various aspects of the lifestyle per say; I have been married multiple times, have an extended network of friends, many I would consider my friends and have had friends during each of those relationships/marriages that were the friends of the wife(s) and or were friends of our as the respective couple. I have had friends that were very conservative, some that were very socially liberal, while others were more in that none of my business crowd. So as you can image, we have had friends that were vanilla/traditional to the point of being a bit judgmental if they suspected something out of the so-called traditional norms; we also had friends which were on the other end of the spectrum that we knew were ‘swingers’; while others were more of that type that wish they had a marriage which was lifestyle orientated.
With that said, only you as a couple truly know your friends. Both ‘Nazareth’ and ‘2wheel’ made good points that you should consider.
As ‘Nazareth’ put in his post; he is recommending that you resist the temptation, no matter how strong it is. Even if you do not share truly intimate details, you and or your wife would be sharing details at a level that would be risky on various levels. This can impact how you’re close and not so close friends view you as a couple or even individually, it can impact your family and even both of you professionally if it became common knowledge.
As ‘2wheel’ put in his post; he was very straight forward by saying “NO!!! Private is private. Today's friend can be tomorrow's foe.” This is something that you should consider when deciding if and whom to open up to within your circle/network of friends.
The safest option would be to develop lifestyle friendly circle of friends for you and your wife to exchange experiences and ideas within. Now with that said, in reading your post a few times, it seems that you as a couple may have multiple motivation for opening up to close friends.
As far as my own personal experiences during my 25+ years of being within the lifestyle; it is good to find balance between discretion, privacy on an intimate level, and being able to be open about the lifestyle with selective friends so that your wife can fully enjoy the lifestyle with greater flexibility. Early on we were very selective with whom we spoke with about the lifestyle activities, we were as discrete as possible, although as you can image the word does get out even if in simple quite silent whispers that you do not directly hear yet you know they are out there. We did reach a point when my than wife opening up for the first time to some of her close friends which were not in the lifestyle. This allowed for her to do what you have indicated that your wife would like to do. Although the motivation was a bit different, as we already had lifestyle friends that we/she could speak with openly about lovers, etc. My close friends were already in the know as they were lifestyle friendly. This truly allowed for much more openness for my than wife; which allows for some guys to be included into social activities, and minimized questions when they were seen out at clubs or the moves, etc.
Yes, you do need to understand that many people will look at you differently and also treat you differently. Just my 2 cents!