A stroke of luck

I'm married great wife 3 children, both my wife and I have great careers. With 3 children and careers our private time together is limited. So, sex is rare as my wife is usually too tired when we get time alone. I get more spare time then my wife, but that doesn't ease her burden any, as I'm mostly free when the children are in school and then working later on when they are home, so my wife is left alone care for them. I get home around the time the children go to bed. My wife is exhausted and so not in the mood for sex. My luck changed when I caught my mother-in-law (MIL) with another man other than her husband. If they weren't dressing it could've passed as an innocence interaction. I only caught them because I was only sent to pick up old files my father-in-law had left at home. My MIL feared my telling her husband of what I'd seen, he'd all the money in marriage and an old prenup as well. She wanted to make a deal with me to keep me quiet about what I'd seen. But I was in a hurry and said after I drop off the files, I would meet her and discuss what she was offering. I usually have 3 or 4 hours of spare time during the day but have to work back later to cover work that came up after hours. I usually go to the gym and work out. But that day I would meet my MIL, she was very worried, so she came back with me. After delivering the files I headed off again with my MIL. We drove back to her place where she offered anything I wanted, my MIL is a great looking woman. My wife gets her looks from her mother and her business smarts from her father. So, with an offer of anything and feeling horny I asked for sex, I'd already thought of the excuse of "I was seeing how desperate you were" in case it went badly. It didn't, that's how I became my MIL's toyboy. Regular sex with her in exchange for staying silence. Funny thing I wasn't going say anything anyway as it would've upset my wife a great deal her parents divorcing. Perfect outcome for me sex and a tired but not upset wife.