Bugsy - have just read this thread for the first time, and am very sorry to hear about what has happened.
A friend of ours was unfaithful with a colleague at work (his group secretary - now we're talking unimaginative) and his wife had her suspicions confirmed by finding things around the house which showed he'd been having sex with her there, confronted him with it and he confessed that the affair had been going on for a number of months. He claimed to have been trying to end it for a few weeks, but as they were about to leave Australia to return to the UK, he had thought that the affair would shortly be coming to an end enyway and she'd never need to know. They didn't have kids, but had been married for a number of years and were thinking of starting a family.
She was immensely hurt, and for a long time no-one was sure which way things would go. She returned to her family for a while, and they both took separate holidays to have a complete break (they had been planning an extended holiday together, and they both still went, but she changed the time of her trip so they weren't together). He knew how much he'd hurt her, and looking back said he couldn't quite believe what he'd done, and made us believe how much he regretted it and how determined he was that if he won her back he'd never make the same mistake again.
It took a lot of work, but they are now happily back together and have 2 kids. I did pluck up courage a couple of years ago to ask her whether she trusts him, and she said not implicitly as she used to, but that she felt he was now less likely to have an affair than someone who had never had one and who therefore hadn't been through the repercussions.
So, while it may or may not be right for you, it is possible to get past these things in some cases. I definitely agree with you on the enormity of the decision you're facing and wish you all the luck in the world in whatever you decide to do.