They both teach at the same high school, but in different departments. He is PE and football coach, she is science. So they would rarely have the chance to see each other at work. This really took off this summer since neither works and my wife started going out more often with friends from work. He happens to be one of the group of 5 - 10 who kind of hung out this summer. It went from there. School started back here yesterday, so by default they will not be texting/calling each other quite as much. I'm sure that one fact helps some, but that will only diminish it during work hours and his practice/games.
And yes, I agree that OM being divorced makes the decision tougher. In my mind, it would be a no-brainer to tell OM's wife if he were still married.
Regarding her family: I think on the surface they would be supportive of the marriage, but if push came to shove, I'm not sure which side of the fence they would fall on.
I would say my marital style has been more controlling.