Do you think a grandparent should insist that her grandchildren receive the Sacraments even though the parents are non-practicing and extremely anti-Catholic?
I do not. And I'll tell you why. Children ,especially, small children are receiving instruction for the faith that directly contradicts their parents views on these matters.
I have a niece, with 2 young siblings, who is struggling because Grandmom has insisted she receive Catholic instruction and even payed for Catholic school and of course that she receive the Sacraments. The child's mother, (the father is not in her life), has given in to all of this to placate the grandmother. But the mother tells her children that this catholic stuff is all nonsense and that there really is no God . The mother is living an immoral life with a boyfriend coming and going so she is no example to the children. Also, the mother, tells the children that homosexuality and cohabitation are OK and that the Church is wrong on these matters.
The problem in all of this, is that the children do love, respect, and want to believe their mother. (I think that is something God put in all children-a need to love and honor your parents) As a result they are torn between God and their mother. They are very young and I don't know about you but I remember my parents being my authority on everything at that age. I really think God made it that way for the good of the child.
Now the niece is forced to choose between the Church and her mother(she doesn't have strong relationship with God) I know she will have to choose her mother. And in this unfortunate situation where she must choose, she chooses against the faith and all it has to teach her. She already has.