As far as the cars go,,
Visit one of those redneck hunting stores and pick up some Deer Scent,
a horrible smelling fluid extracted from a deers ass, that will make a dog puke.
Squirt it on both doors driver and passenger, and be sure to deposit some into the ventilation vents directly infront of the windshield. And if they leave their windows down,,, apply a generous sprinkling into the carpet and seats.
They will sell those cars
If they ever get the stench out,, they should start protecting their cars by parking inside the garage after that. Repeat if necessary and blame it on the local wildlife.