[good times]

Personally, I think this is a bad idea for a number of reasons.

The most important are, we never play with anyone from work. Can she afford to lose her job? Because you have to consider the fact that it is very likely that everyone at work will find out about it, whether the guy accepts the proposal or not.

From what you said it sounds like this guy is not a swinger. Most non-swingers don't understand swinging at all. My guess is that two things would happen if she were to approach him for sex. He would probably initially freak out about the idea, and within a short time, everyone he knows at work will find out about it. A non-swinger has no compulsion to be discreet, unlike someone who is a swinger and knows the rules.

Finally, I would highly recommend that you initially experiment with swinging together and with other people who are already swingers. They are not hard to find, and a lot of potential problems are mitigated by the fact that they are already swingers. Furthermore, swingers will be sensitive to your concerns and be ready to stop if you or her should have any issues during your first full swap experience.