I am really shocked by the attitude displayed here by some posters towards Granypie. She is concerned about her grandchildren's lack of education and is attempting to do something about it; the fact that they appear to be lacking age appropriate skills in literacy and numeracy does matter and needs investigating. Unfortunately, the inspection of homeschooling is very limited and restricted in what it can achieve, and can only offer advice to improve a poor situation.
Their father needs to take far more responsibility for his children's welfare, and moving a long distance away from them is not going to help. but I do not think the grandmother is using the situation to vent her spite on the daughter in law.
'Unschooling' follows loosely the principles of child-centred education and independent learning, which works for some children, but fails many unless there is an underlying structure for assessment in place. I heard John Humphrys once investigating various forms of primary education, in Wales and at the end of the programme he declined to say which form of teaching he thought best, but he did know that children only got one chance at schooling, and it was important to get it right, because lost time is very hard to make up.