Grandchildren in care

My 3 young grandsons have been taken into care, I have offered to take them but failed the assessment due to them being 150 miles from me and a load of nonsense. Social services are now threatening to have the children adopted. I feel so useless because I can't do anything and am really worried about my daughters mental health if the children are taken away permanently as she has a history of self harm. I haven't slept in weeks and don't know where to start.