The first thing you truly need to decide:
Do you want to save your marriage for your kids' sake or because you still love your wife and want to be with her?
Look deep into your heart and be sure before you answer that question. The road you must follow to save your marriage is long and can be very hard. Be sure it is the road you want and need to travel.
If you truly want to save your marriage, your first step is communication, honest, deep, even painful communication. You need to discuss what has happened and what each of you want and need in order to continue as a family. Do not argue. Discuss it with open minds and hearts. I suggest these conversations take place in neutral territory. A restaurant, a park, where ever you are comfortable, but not necessarily in your home territory. Often people become extra defensive when on their own turf. You have to tell her honestly how you feel, and you have to be willing to listen to how she feels as well.
This will not be easy, nor will it be fixed overnight. But if you can get through this, you may find your marriage will be stronger and more secure than ever before. Good luck.