Not sure how to search for something this specific. I can easily find cheating stories just that added wrinkle of the kids choosing sides that I can't figure out.
Specifically I am looking for stories where either 1) one of the parents cheats, the kids either know or aid the cheater, there's a divorce, and the severing of ties between the innocent parent and the kids... OR 2) the children aid the innocent parent in getting the divorce, sever ties with the cheater, and may even help the aggrieved parent find new love.
May be that I am too specific on this one, just like the added "meat" of the kids being involved in the destruction of the relationship. If I am too specific then just go with stories where the kids are somehow involved.