80s or 90s movie, couple stays with weird family with child like adult children

[JJWX]

Saw this on VHS or cable many years ago.  A couple stay with a dangerous psycho family, the adult children behave like young children.  The son is chastised for playing on dangerous swings (i swear it was Michael J Pollard, but evidently not), and the adult daughter shows off her baby, which is a doll.

[M.10rda]

AMERICAN GOTHIC is a late-80s horror/comedy w/ a weird family that does include the one and only Michael J Pollard.......

Alternately, there's the early 80s SLAPSTICK OF ANOTHER KIND, a truly grotesque sci-fi/horror/comedy/living nightmare which includes giant (alien/human hybrid) toddlers, including one played by Jerry Lewis in gruesome Frankenstein-like make-up. The oversized toddlers affect hideous baby-talk accents, making them sound sort of like Michael J. Pollard, I suppose. I dunno, obscure though it is, I feel like one would remember SLAPSTICK OAK more clearly/specifically. I have mentioned on this site previously that it was the first Worst bad movie I ever saw, and I suspect I would still feel the same way, if I had the ignorance and lack of self-preservation necessary to revisit it... 

[claws]

AI thinks it is:

The Baby (1973)

Other possible candidates:

Mumsy, Nanny, Sonny & Girly (aka Girly, 1970): A British horror film about a family where the adult children act like little kids, playing twisted games. The daughter shows off dolls and toys, and the son is infantilized.

Spider Baby (1967): A cult classic starring Lon Chaney Jr. about three orphaned siblings who suffer from a genetic disorder that makes them regress mentally into childlike, violent states. They live in isolation, and their behavior is both childish and dangerous.

Most likely answer: Girly (1970), also known as Mumsy, Nanny, Sonny & Girly. That matches the dangerous psycho family, adult children acting like kids, the swing punishment, and the daughter with a doll as her baby