Let me share my own experience, for whatever it's worth...
My wife and I had tried swinging "before" and stopped when we decided to start a family. Some years later, our marriage hit a low patch. She had a one night stand, in part to break us up. It didn't work out as she planned. Instead, we reconciled, we talked, we rebuilt trust and eventually got back into a good place with our marriage. Later, we started swinging again and it's been great.
I'd say you have to separate swinging and cheating in your mind, because they are two very different things. Cheating, for me, is something that happened when our marriage was weak and broken. Swinging is something we do now that our marriage is strong and whole. All relationships have their ups and downs. If you feel yours is in a place of strength, than do things that you enjoy together... including threesomes and kinky sex if that's what feels right for you. If, on the other hand, you have the idea that swinging will somehow prevent cheating, don't do it because it won't.
My $.02. Take it for what it's worth.