That would be fun.
In the UK, it might be possible for the girl to be 17-18 (the age of consent is 16), but a hot, busty MILF in her late 30s-early 40s being tickled by a bizarre old couple into their eighties would turn me on. I had an idea, based on such a couple who run a hardware store or flower shop. The place would be very ordinary and unassuming, and the couple very genial, perhaps a bit too friendly and touchy-feely, but sweet. I imagined Lucy being offered tea and cakes in their back office, and both of them sitting and watching her as she ate, like Mr Alexander in A Clockwork Orange. it's creepy, yet also funny as she tries to make light conversation, and they start to gently tickle her bare arms, neck and between the shirt buttons, making her spit cake crumbs.