Didn't the guy on the path say that a bike was blocking the path? He said that he had to swerve around a bike, not that he leaned the bike against the fence. Other information is that the bikes were leaning against the fence, so it seems that the 12:27 sighting may not be credible ... especially if no one has come forward claiming to have moved the bikes. It seems to me that police need to go back to the last credible sighting at 12:15 and start again from that point.
Regarding tips from the public, so often tips come in that are not related to the missing person ... so I'm skeptical of all tips from people that didn't know the children.