@echomaren,
Do you have visiting rights? When's the last time you saw them? Do you communicate with them regularly? How much interest have you shown in the last 3 years?
The thing is, if the attorneys, social workers and case manager recommended it, they could be right.
Are you sure you're able to look after them?
I don't know what 'signed rights' means exactly, either. Could you not call a Legal Aid lawyer and ask? Or maybe look it up on a government web site.