Meanwhile, back at the ranch . . .
Playfulgirl, a couple of things:
You will never fix a troubled relationship by adding complications to it, and polyamory is complex.
If you want to find a path to healing in your relationship(s), you and your partner need to discover and address the issues that lead up to the cheating, deal with and heal the wounds, and find solid ground for the both of you before introducing additional lovers into the situation. If one or both of you are not ready or willing to do the work needed to set things back on a healthy path, then, sadly, it's time to cut your losses and move on.
Also: I get the impression, you think polyamory is a form of swinging; it is radically different. Poly is WAY more than sex, and swinging is basically JUST sex. Polyamory involves loving, involved romantic relationships between multiple adults. Poly is based in honesty, love, and respect for all parties concerned. Swinging is just fucking around, IMO.