Childline counsellors have extensive training, references and checks. They are not alone in the room when they take calls , they can be overheard by other staff and sometimes a supervisor.
Call notes are checked by a supervisor and keep securely . Children who call regularly might usually speak to the same person, but that is carefully supervised.
It would be almost impossible for a counsellor to groom or abuse a child through child line .
A referral to social services is a management decision and is very rare. What the boy said must have raise serious concerns. Of course that doesn't mean that it's all or even party true and of course children do make false allegations for various reasons. Sometimes they tell of real abuse but lie about who the perpetrator is.
Nothing about this sad situation indicates that the OP or someome in her family IS or ISNT abusing her child. All it tells us is that her oldest child has said things that are serious.
So could people please stop inferring that it must be true. None of us know enough to judge, perhaps not even the OP as she's not been given the details ( this is perfectly plausible BTW) .
OP I'm sorry for what you are going through and hope you can get legal and practical RL support soon.