Review of The Lodge

So what if my ex-wife, the mother of my two young children, blew her brains out just 7 months ago after finding out I'm marrying my new, teenage girlfriend. I think I'll take my grieving kids and said new girlfriend, the only surviving member of a suicidal cult, to a remote cabin, then leave the three of them there for several days while I run a work errand. What could possibly go wrong?