From what you have mentioned, it sounds like what ever your son has been discussing with childline, has triggered them to contact the police and social services, as they have concerns for him and his siblings safety.
Therefore, your children have been removed from you until social services can conduct a full investigation and ensure their safety.
When the children left were you given any paperwork, or advised what the next steps would be?
I understand that you are upset and angry, however your children wouldn't have been removed if there wasn't a threat to their safety.
Can you think of anything that would trigger safety concerns? Such as arguments between your son and yourself, or your son and your partner, or arguments etc between you and your partner?
Try and take a moment to think about what is happening at home at the moment, and work with social services to change things if needed.