WMG / You're Next

Hotline Miami is in the same universe as this movie.
The reason animal masks were chosen as a disguise is because the Animal Mask killings in the Hotline Miami games from the '80s and '90s have become ingrained in American culture. Everyone knows about the animal masks, campfire stories about them are traded among children, and Halloween costumes of them are popular even.

The easiest way to have everyone assume that it was just lunatics killing a family would be to appropriate that mythos.

Erin knew Kevin McAllister.
That, or her Crazy Survivalist dad showed her Home Alone a lot growing up. Either way, it explains why she'd think to Booby Trap the house so thoroughly.