It's a controversial subject, Nav. I certainly wouldn't LIE to them, if asked directly. I would NEVER lie to my kids!!
I can only tell you what I did. Once I had proof of my wife's affair, I immediately exposed to our two adult daughters, then 18 and 20. It turned out that the 20 year old suspected it, and the 18 year old had actually KNOWN about it for several weeks, and was afraid to tell me because she knew I'd be so upset!! The poor thing.
A couple of months later, after my wife still stubbornly refused to end her affair, I then also exposed -- in an age-appropriate way -- to my S-then-14. I asked him if he knew why Mommy and Daddy were fighting, he said "no." I asked him if he wanted to know why, and he said "yes." So I told him that "Mommy has a boyfriend, and married people shouldn't have boyfriends or girlfriends other than their husband or their wife. And that I was hurt by it, and disagreed with it, and asked her to stop, and she wouldn't, and that's why things were so tense around the house lately.
"Oh," he said, growing quiet. After a long pause, he said "It's that guy from the gym, isn't it."
