It is possible that everyone has lied to both LE and the media. I myself have been involved with two newspaper articles in which the facts were not accurately reported. Sometimes it's due to the rush to get info out, or get the scoop, or just because of a lack of due diligence. And we've all heard of LE scenarios where they completely screwed up--failed to secure a crime scene (Ramsey.), etc. It serves is all well to be skeptical until evidence is produced and even eye witnesses are unreliable.
That being said, it would be incredibly easy to provide proof the children are safe. If they are in hiding due to custody fears (which, in their delusions, they may believe whether or not that's the case), they could then negotiate further with LE through their lawyer, stating their case to maintain custody. That they are not pursuing those angles, if they are innocent, does not make any sense, in my opinion.
Lots of dead bodies under suspicious circumstances doesn't help, either.
Can you provide a scenario where "acting really guilty" makes sense? Or even where hiding makes sense?