I'm all for the inclusion of Trevor's other creatures in this lore! That said, though, Siren Head was responsible for the children in that case. I mean, why else would Riley be on such a revenge streak against it?
But that said though, I wonder if either of the rangers smelled cinnamon or heard a strange creaking noise in the skies above before the events of 1988? Perhaps they should have taken the warning when it was presented to them.