Damn also thinking about scene variations
Like mom drunk get drunk as fuck, and son can both do concious/unconscious fucking, whole trip, filling her as much as he can before reaching the place
Or mom had a fight with Dad about making another baby and takes son instead as he'd have the closest resemblance to daddy on some crazy shit
Or son takes advantage of mom by blackmail or something because he caught her cheating and is threatening to tell, but decides to have her buy his silence and then becomes addicted to his cock being double the size, and the taboo it has, cause she's a secret nasty slut.
But ya, it's fun to theory craft and make scenarios, curious for more details