A/N: For legal purposes any characters directly shown in a sexual position are aged up for your jurisdiction.
Vanzilla is an option:
"Dude why is the van shaking?" Luna's eyes narrowed at the disturbing shakes of the family van, the windows suspiciously covered.
"I don't know Luna, but I can find out!" Lincoln declared, a finger extended with fateful confidence. Sneaking over to the van in case the mysterious occupant had a peep hole, he determined with Savvy-like deduction the centre of the movement was coming from the sweet spot.
He smirked, and motioned Luna over to the broken locked seat directly opposite said spot. "Whoever is in there is really distracted with whatever they're doing, I bet it's Lynn eating the leftover dessert again!"
"Hunh?" Asked the clever and insightful Luna with the same whispered tone. "Why's that dude?"
"Listen," he cupped his ear and Luna did the same. Sure enough there was a semi-liquid sound reverberating through the vehicle, mixed with deliriously happy murmurs. "What else could that be? But this is the last time we let her get away with it! Come on, I'll get a photo and you grab her so she doesn't turn me and my phone into a pancake!"
Luna's eyes widened as comprehension hit her, but even as she went to stop him his left hand had already produced his phone with the camera app open, his right gleefully flinging open the door to reveal-
Lori.
Lori with Bobby's half dressed image on her phone.
Lori with approximately none of the shorts and pants the siblings had so dearly wished she had been wearing, and her fingers sadly not so hidden. The three stared at each other with regret, but none so much as Lincoln whose trembling finger unwittingly pressed the photo function.
Hours later Lori was thankfully not in trouble (at least with her parents) because Lincoln and Luna had agreed no one wanted to discuss this, though Luna had privately roasted her about violating the 'desecrating shared spaces' rule she herself had established. She had shamefacedly apologised in an elder sister meeting, and agreed to replace Lincoln's phone. Rather than bothering to delete the image the eleven year old had sensibly snapped it in two with trauma driven strength and pulverised the remains until he felt the picture was history.
Lincoln meanwhile was in his room, calmly rewriting the sweet spot diagram to include a 'hazardous material' sign over the now former best seat in the van (for Lori had been so inconsiderate that she'd not even laid down a towel), before chucking his pen aside to sob into Bun Bun for the night.
What about using the Garage?:
Rita knocked on the garage door, getting no answer over Lori's oddly loud music to her annoyance before popping in anyway "Hello sweetie, just letting you know that dinner is-"
There was a terrible silence, and a worse sight.
"CHASITITY BELT TWO WEEKS!"
"But Mom!"
"Three for talking back!"
Why not use Lisa's Bunker?:
"Don't even try it elder sibling; your escapades have scarred our Mother and Brother, I shall not add my own place of work to the list!"
"But Lisa-"
"No buts you utter degenerate!" Lisa glared upwards. "My experiments are very sensitive to foreign matter and if I find even a hint of your 'emissions' anywhere near them I shall neuter you in your sleep!"