This isn't one of those Do-Over fantasy stories. It's a Do-Forward! Peg and Frank (40s) wake to find they have renewed bodies (20s) in present day LA. They need new living styles, moving north to Portland is the answer. In Oregon, they learn who caused their changes, including their runaway libidos! [OP: This might be one of my best.]
Who gives this bride away? First her father, then her husband. This wedding was one for the books! Daddy didn't know what hit him. At least his other daughters' the bridesmaids were behaving. "GODDAMMIT!" Wrong answer! "I GIVE UP!" Let's get this party started!
The widow Margo Needy prepared to send her adopted son Elliot off to Paris to a college program for high intellects. Left alone in the wilderness mansion of her late husband, college basketball coach Darryl Needy, she opted to let her son's young friends rent spare rooms to feel safe. Let her secrets and theirs lead Momma Margo down a gloriously erotic path that goes darker by the day. It was time for Margo to let it all hang out. Just like it was time for those boys to become men. BIG TIME!
The story describes the accounts of Tom after his discovery of a drug that emulates the response of the female brain to ovulation and enhances it 1000x.
It makes women horny beyond control, releases eggs, makes them pregnant even if on hormonal birth control, numbs the gag reflex and pain of deflowering, among other things.
Tom discovers slowly how to use this drug to make a living, entertain a growing harem, cuckold, and ultimately spread his genes around the world.
My take on the (maybe not so) innocent neighbor girl falling into the clutches of a "dirty old man." This is supposed to be a one-off, but I reserve the right to change my mind on that if more ideas come to me.