As Cadet says your story is very similar to many others here like mine.
One important thing to keep in mind is that despite some appearances of reluctance your wife is 2 years ahead of you in thinking about this and planning it. This isn't something that happened overnight. It takes deliberate thought and a series of actions repeated over time for her to have gotten to where she is right now.
Now - before I go too far, I want to be open about the fact that I didn't save my marriage. I know that is what your focus is on right now and that's fine. But my comments may be slanted in a direction that you don't want to hear.
From the brief bit that you have shared thus far I think that it is indeed safe to say that you have a WW vs a WAW. The selfishness, the lack of thinking through actions and consequences all point to that.
The first thing you need to do is to protect yourself and your kids. If you haven't done it already, get tested for STDs. People who do the selfish act of infidelity don't worry about the consequences for others.
Even if you don't separate finances see if you can set alarms on the bank accounts. For example I get a text on any bank transaction over $100 and on all credit card transactions. While it won't stop any chicanery it can give you a heads up like when my ex removed a large portion of our savings account without discussion or agreement so that she and OM could go on a tropical vacation.
Educate yourself on divorce law and your rights and obligations. Don't expect your W to be helpful or cooperative. Some lawyers will do a free consult.
Make friends with people like your banker and such. Do you have any IRL friends who you can talk to? I was astounded that when I was going through the worst of things who was there to lift me up when I reached out my hand. Also see if you can get yourself into counseling. The professionals can help you build the tools and skills needed to survive this.
Right now she's operating on a high that she's "getting away with it". This isn't about you or even OM. It's about her and her selfishness.
Stay strong. You need to be the sane parent.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells
