i was thinking a HA but this time its nanny and frank and wendy finds them haveing sex and then joins in

How about Wendy finally getting out of the darned house once in a while? She's got to escape sometime, and dear Nanny doesn't wield quite so much power out there in the real world. And maybe Wendy can grow to appreciate Nanny's protectiveness if she's rescued from a Bad Experience.

If you're afraid of getting too edgy, you can just find a way for Wendy to slip out of the house and avoid Nanny's search efforts. Whether of not Wendy's got time to charm a boy, and remain uncaught, is up to the player.