9.30pm curfew biggest plot hole? (spoilers)

The biggest plot hole is that why didnt he lock grandma in her room at night instead of just letting her out for the kids to see if he or they didnt want them to notice anything...its just bad writing cause if he had locked her in, we wouldnt have a horrible horror movie infront of us with plot holes bigger than Icelands hot springs...

Lots of insane people are self-aware, in real life and in the movies

Remember the big surprise in "Cuckoo's Nest," where most of the patients admit that they're there voluntarily.

Nana & Pop-pop are aware of their limitations - they take great pains to stage a "perfect weekend" for themselves, including hiding as much of their nuttiness as they can. They're just not entirely successful.