I would put money on their class mates knowing and not wanting to get involved - don't expect support from there. Their classmates' embarrassment will make them just ignore it all.
I think your eldest son's condemnation of his mother would have more clout if you are willing to give him that information. My kids were 15, 13 11 and 8 when they found out. I don't know if it is right to lay that burdern on their shoulders; I was just so shocked that I didn't think about keeping my voice down, I say now with great shame. However it did resolve things.
Well, they've gotten really close to each other and have been going out to bars on weekends (remember my wife is acting single right now).* But you're right, if they're part of that lifestyle, they probably won't care, and won't "judge" her.
*They still maintain their affair secret to their classmates even though they go to the same social events.
