celeb there would have been a safeguarding meeting with health, education, probation/police and the grandparents would have been able to attend any part of it that wasn't confidential e.g. discussion about police or probation management of a man (the children's father) who has used a knife to threaten social workers. A risk assessment to gauge who would be at risk in what circumstances would determine the protection of the children, hence the placement with a foster carer where the children's father couldn't find them whilst there remained a risk to safety - people in authority appear to be at risk from him i.e. teachers, social workers, family GP if they needed to visit. Children could be caught in the crossfire if he turned up with a knife trying to find them, or with a grievance to express.
If the grandparents could have been ghosted away somewhere where they were anonymous and could protect the children in such risky circumstances, all well and good, but grandfather chose to appear on a TV talent show, and this would make him easier to track down.
Sounds like both grandparents and impolite social workers could have tried harder for these children, according to what was reported in the article, but they seem to be safe with a foster carer in the interim.
Local Councillors gone so far, Reform

. Went to the gym but didn't get my usual trainer had the owner and what a task master he is. Thought he was trying to finish me off
. Now had that happened yesterday when I was having a bad day I may be wouldn't have minded too much. Managed to get through, but only just. He told me by the end of the year I'd be cover girl material. I told him I thought he was a personal trainer, not a miracle worker
. 
Posted our card through their letter box this morning, my bro posted his and my mum's through last night. Just had 'phone call from my bro to say both cards have just been put back through their letter box by our d.i.l. He recognised her voice but wasn't in time to see her before she left. Their card had been opened (they obviously hadn't recognised his hand writing) and ours of course had not.
. That's what really annoys me, they are depriving a little 2 year old of cards from his gparents, great gran and great uncle. Using a little 2 year old to inflict pain and suffering on others. Our s has spent the last 18 months lying about us and portraying us as bad people while simultaneously using his only child as a weapon
.
I have no doubt whatsoever that my s knows how we feel which is why he does these things, or as it would now seem gets his wife to do it for him.

