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.