Cheating is not subjective. Every time I have heard that statement it came from a cheater.
Go ahead, have sex with the couple without your wife's knowledge or permission. Then tell her it was only sex, not cheating, because it was not emotional or romantic. Let us know what she and her lawyer say.
While you may not agree with this communities morality, ethics, or differentiating between swinging and cheating, you did come here and ask advice. Take it or leave it. We share everything with our spouses, yet you call us hypocritical for not telling the general public what we do, while you contemplate having sex with another couple behind your wife's back. Now that is irony.
Focus. Okay here is some focus for you. Grow a pair and ask the other couple if they are swingers and if they are interested in playing. If they are, ask your wife if you can have sex with them. Then you will know and can decide for yourself if you should have sex with them. That way you don't have to suffer the derision of a bunch of hypocrites. Focused enough?