Proceed as if he's still in contact with her, and lay out those boundaries you feel YOU need in order to live peaceably. I will warn you, however, once a cheating spouse either self-confesses or is exposed, it drastically changes the whole dynamic of boundaries. I realized this in an "oh my God" moment with my sitch, when suddenly I realized I couldn't really attack the affair anymore, since it was now exposed. Like the foreign-policy hawks after the end of the Cold War, I was left with this gnawing "NOW what?" moment.
All I could do was expect her to let me (and esp. the kids) know when she'd be home, not spend our family's assets on her affair, and not call or text him from inside our house or in front of our kids. That was about it.
