You can do all that... but will it change anything for your family?
If you're doing this altruistically, thinking you're the ones that can stop this happening to another family, I wish you strength and resilience... you're going to need it, because you'll have to do better than all the rest of us that have tried.
If there is a direct good that can come from complaining for your family, then go ahead. But if you're wanting an apology? Very unlikely, I'd say.
My experience was shocking. So shocking it's made me question everything I was told about BPs, and DC's histories etc. It's hugely concerning. However, it's not unheard of for it to be turned around that you're the problem. And when children's services decide you're the problem, that can be a very scary position to be in.
Be very clear what you want to achieve. And as others have said, don't expect the process to be as if it were a functional organisation. From what I've heard of the NHS 20 years ago, that's where social services are still, cover-ups, denial, blame the victim.
Good luck.