I am so sorry to hear about your sitch. It's so hard when there are young kids - who are confused, don't really understand what is going on and are easily influenced...
I have to say that having H leave was tough, finding out about OW was tougher, but by far, the toughest thing of all, was having my kids exposed to OW and spend time with her. So I get your pain and I don't wish it on anyone - even my worst enemy.
While I agree 100% that exposure to OP is completely inappropriate at your stage, it will be very hard to restrict / enforce that. My H exposed OW right away to my daugheters who were 3 & 2 and our then newborn son. My L told me there was nothing I could do (I live in California, where infidelity and things like exposure don't really matter much in the legal system and D process).
I made sure to let my H know how i felt when it happened. It only made things worse for my emotional well-being. He could care less and in a way, it only pushed him to do it more.
It took a long, long time, but I let that go. Not because it was ok, but because it was out of my control and because in the end, obsessing about it only hurt me.
I know that is probably impossible to do so early in your sitch - things are so raw, but any and all steps you can take to take care of you emotionally will bring you closer to that point.
Remember - you are their father and no one will EVER take your place. Show your kids how amazing you are and give them the example of strength and grace in the face of the worst adversity... Placing all your focus on your kids will also help you detach - which is very, very hard to do, but so necessary.
Stay strong - you can do this.
Me & H: 44 D7, D6, S3 Together: 20y, M: 17y EA: 11/13/10, Sep: 12/23/10 EA becomes PA: Spring 2011 H filed for D: 09/06/12 D Negotiating began 2/15 OW seemingly gone on 3/15 Still negotiating D
