I want an older friend to fuck my wife

I have a fantasy about my wife being fucked by the husband of one of her friends. I think they must be in their late 60s at least, and retired. We have spent time at their house and also visited them on vacation, and my wife is quite fond of them. He is not very tall, with grey hair, glasses, tan skin from as life spent outside, and he is fairly rotund - he's had his shirt off around us on more than one occasion. I like to imagine he's thought about fucking my wife before, she's worn a swimsuit around him so he's definitely seen her prominent cleavage. I'm sure he'd be very happy to get a chance to play with her naked body, fondling her big tits and sliding his fingers inside her. Climbing between her legs and sliding his cock inside her, pumping her slowly and deliberately until he grunts and empties his balls into her.