It has to be Tylee and JJ. It can't be anyone else. They had to have had a tip with the exact location IMO. So it had to be Lori realistically, unless Chad has done a deal to get the lesser charge of evidence concealment. Only those two would know the location IMO.
Unfortunately I see a defense here. Alex killed them on his own, Chad disposed of the bodies, and Lori only found out after the fact. That makes her innocent of the abandonment charge, her only felony. Both are innocent of murder. So they only charges anyone would be convicted of would be a few misdemeanors of lying to police. Yes, Chad is facing a felony with a five year maximum sentence so he would do some time but I doubt 5 years. We'll see.
I don't think that is how it went down. I just think that is the story they will tell. Most people here are convinced AC did the actual killings so I don't think it will be hard to cconvince one juror that iss what happened.