Boy, so much went through my head when I read your question. We decided to give swinging a try about 4 or 5 months ago, after 18 years of monogamous marriage. It has made us so close that I now have trouble remembering what it was like to be a typical couple. I can tell you only what we have discovered about ourselves, but the main thing is that if you have a solid relationship now; it will only get better through swinging! That is because the real treat in all this comes from the increased honesty, communication skills and self-confidence you will develop from your experiences. This, by-the-way, translates into the best lovemaking you and your significant other will ever have, but it happens after the swinging encounters! You will never find someone who can push your buttons like the one you love.
That being said, here are a couple situations we found ourselves dealing with;
We developed set boundaries before our first “club” visit and thought of every situation; Wrong. We focused so much on figuring out what level of sexual contact each of us was comfortable with that we did leave something out, simple touching and kissing. On our third or fourth visit to the club, we were finishing up in one of the “play” rooms with another couple and my wife offered to run to the bar for some waters for all of us. Simple enough, but on the way home she told me that the bartender had given her a kiss (not just a peck on the cheek mind you, tongue and all)! That really bothered me even though I had just watched her go oral on another man. Funny what can bother you sometimes… It came down to the fact that something had happened between her and someone else without being forewarned or me knowing. It made no difference that it was only a kiss, I felt cheated on for just an instant.
Another thing that recently occurred was with a couple we are very close to. We have even discussed going “all the way” with them. Currently we are what you call “soft swap; touching and oral” only. She had said that while she really liked the other couple's guy, she was not quite ready to go further yet and would let me know when she was. Well, we ended up in a nice hotel room that had two twin beds in it. Things got started with everyone on one bed, but then we split off into the two beds. About half an hour into things, I glanced over to my wife and it really looked like she was going “all the way”! Even though we had talked about the possibility, I felt like I had been kicked in the stomach because she had told me it wouldn’t happen yet.

That sort of thing is a big step for us and I was not mentally ready. Turns out she was not doing what I thought and quite literally had everything in hand= LOL.
The point of all this is that you have to be ready for things to happen (or look like they did) that you did not plan on happening. How you deal with these issues will determine if you are, in fact, in a strong relationship with solid communication skills. In our case, these situations have made us stronger because we have touched the deepest parts of our insecurities and survived. The steep learning curve is worth it!
Enjoy the adventure, but don’t forget that there is no such thing as an adventure without risk!
Let us know how things turn out...