My guess is that Elusive is absolutely right. I think your wife is interested, So. Gentleman. If she weren't, she certainly wouldn't have shared this information with you.
The first problem you need to solve is that fear to communicate with your wife. On our second date, also the second day we'd known each other, my wife and I made an agreement to never be angry at the other for asking a question, no matter what that question may be. You need to tell your wife of your fears to talk with her and get that problem solved first. Once you share both your interests in swinging with each other, your communication will be more rewarding than you ever dreamed and getting into swinging will be no problem at all.
The next problem I think y'all
may have will be bringing in the other lady's husband and that will probably be easy because my guess is that he and she have been talking about playing for a long time. In fact, they may already swing. Y'all could find yourselves with a lot of new friends!
Mr. Alura