I think the queasiness will settle and eventually go away if you work on strengthening and developing the relationships that exist among you rather than focusing on the sex. Examine and talk about how the dynamic has changed between you and your wife now that there is someone else she is intimate with. Get to know this guy as a person. Go out and do friend stuff with him. Make the time for each of you to nurture the connections separately and together and, perhaps most importantly, outside the bedroom.
The world opens up... when you do.
"Oh, oh, can't you see? Love is the drug for me." ~Bryan Ferry
"Love and the self are one . . ." ~Leo Buscaglia "