Too bad there weren't any grandparents living w/ them (Alternate ending)
Okay, so we learn that loud sounds cause pain to the baddies, thanks to the young woman when she starts up the turntable.
But, uh oh, the generator runs out of fuel. What to do? What to do?!
Well, Grandma or Grandpa would know they could keep that awful sound, er, loud music going merely by manually turning the LP fast on the turntable (finger near the spindle, on the label, moving the LP in a circular motion).
As they're taking turns doing that (alas, they are weaker than they used to be 😩), the 'youngsters' go out, get into the truck, and then drive it up to the front door of the house (with a CD or tape turned up full bore) while also laying on the horn so the Grammies could make it into the truck, too. (Sure, Patrick blows up the generator, too; that's s kind of a given.)
We then see them look into the rear-view mirror, observing briefly the baddies they left behind who will now have to seek more hospitable Humunchables.
As they travel on, Lu peacefully goes to sleep until (yes, still alive) Patrick wakes her up to see their new valley/home with the sun rising brightly (a wonderful beacon of hope for a future -- hooray!)
THE END.
With age comes wisdom -- or at least it used to.
-Zzzzzzz