Wait, I'm confused...

From what i could tell the kids weren't involved. The big "twist" which i suspected immediately after the antagonist husband appeared with his tongue cut out was that Everett's wife was the evil mastermind.

One thing i was somewhat confused about was if Holly's husband was a willing conspirator who was betrayed or merely a victim being blackmailed/coerced like Holly & Everett. I'm leaning towards

I wondered that, too. Towards the end, she did receive that text from her daughter saying "Destroy the phone, Mom."

But it seems it really wasn't from her. Not really clear. She (the daughter) was not around in the end, so I assume Lydia sent that text to give her some encouragement?