There is a golden rule for grandparents everywhere , and it is this ...." Your relationship with your grandchildren is entirely dependent on your relationship with their parents - BOTH parents".
You make it very clear that you dislike your DIL - and she is the mother of these girls. Unless you start having a better relationship with her, nothing will ever change. She is the mother - she has the power in this relationship. You can say all the negative things you like about her, but if you don't improve your relationship with her , your DGD's will grow up and not know you, no matter how much you love them.