@Panik_HeavyHeart This is why it's important to have close male friends. They will keep you in touch with your masculinity and will remind you use the pair that you have. The only right thing you have done is not confront.
Here's my advice:
1. Read "180", "No more Mr. Nice Guy", "The Married Man Sex Life Primer by Athol Kay". These should help you become an improved version of yourself. THIS IS NOT FOR RECONCILIATION.
2. Infidelity is rooted in deception and thus it can never, ever be justified. There is not a single scenario. Realize that this marriage is over.
3. Have some pride. Are you seriously going to use words like understand and forgiveness? The goal isn't to necessarily avenge anyone, but act with complete selfishness in improving your and your children's life. You no longer have a wife. Take all you can.
4. Don't confront just yet. Use this time to gather all the evidence, and start improving yourself quietly by working out, and dressing better, and then go talk to all the best lawyers in your area. You'll pay a consultation fee which isn't too high, but it will mean she can no longer have them as her lawyer due to conflict of interest. Also when confronting, don't be too public about it for your sake since it's a small town. Reveal it to her dad, and a few other key people.
5. Serve her the papers when she least expects them, and find a way to be the best dad you can be and set an example of a father that acts with strength, courage, honor, and integrity. And when you heal a little, find yourself a good woman.