For a person with mixed feelings, my advice is:
(1) For the first time, make sure you're present. You might only watch. Or you might get involved by doing whatever your wife and her lover tell you to do. Being present will make you feel more included and prevent your imagination from running wild. Feeling excluded and imagining the worst can feed negative feelings such as jealousy. Once you get used to the lifestyle and no longer have mixed feelings, you can revisit the idea of your wife meeting other guys alone.
(2) After the first time, plan to give yourselves a few days to let things sink in before talking about any issues. If the experience makes you upset, you will have an almost overwhelming urge to talk about it immediately. But your emotions at that point will almost certainly get the best of you. You are likely to end up in a fight. Realize that by waiting awhile, two things will happen: (a) you will calm down and be better able to deal with any real issues, and (b) you will have a chance to see that your wife still loves you and that your relationship is still intact (which will help put any issues in context).
Good luck!
FUCK MY WIFE!
CLICK BELOW TO FIND A BULL