True, if there was strong evidence of a crime. But CPS does not need the same level of evidence that the police need to make those kinds of decisions. If LE is still working on their case and still gathering evidence and waiting for forensics, but they have strong suspicions about one of the parents, I can see why they might go to CPS to get some quick help.
Just for example, just speculation, let's say one of the boys told a teacher that his dad [ or his mom] was asking them to lie to the police about something. Maybe they saw one of the parents messing with the window screen that morning, but were told not to tell the police. That would not be enough to arrest anyone yet, but it may be enough to protect the boys from that parent for now.