The 14 year old boy NAME_1 is regularly spying on his 32 year old mom NAME_2 and his cute 13 year old little sister NAME_3 to try and catch them naked. NAME_2 agrees to be NAME_1's wanking material so he doesn't spy on her or his little sister when he gets horny.
Next day NAME_2 comes into NAME_1's room to wake him for school. She notices his morning wood and already knows what's coming next. "Good morning, mom. I'm horny. Close the door and get naked, please.", NAME_1 says to his mom. "And put on this blindfold, will you?", he adds. While she's kneeling in front of him, naked and blindfolded, NAME_2 hears him jerking off and quiet shutter sounds of a camera. "NAME_1, no pictures, please...", she says. "Here it comes, you slut!", he exclaims, cumming on her face and tits while taking pictures. "Sorry, mom, spur of the moment.", he apologizes.
Flesh out and embelish the story. Start with NAME_2 naked and blindfolded, kneeling in front of NAME_1.