I opened this this morning sure that it would be a JW family, but there was no mention. I just read an updated article where it was confirmed so hopped over here to see what was being said.
Taking a gravely sick child on a last holiday I find to be hugely irresponsible. If that was the case, then hospîtals will work with the family on that and there are organisations which organise family breaks for children in this situation.
If they are trying to avoid blood, then heading to France is not going to work in their favour at all. French law ensures a child gets full medical treatment whether it goes along with a family's beliefs or not. JW parents would have no say in whether their child got blood or not. And if they had JW family in France, then they would know this already.