I've volunteered for a local animal sanctuary for years, and helped many families with cat adoptions. Based on the experience of the sanctuary I have been with, I recommend that you let your granddaughter and her parents select a cat/kitten themselves. If you would like the animal to be a gift from you, then a fun way to do that would be to get your granddaughter a cute book about kittens and write her a note saying you'd like to make a special date with her to go and pick out a kitten herself. Then plan for a day when you and your granddaughter and her parents can go together to at least a couple of local shelters/sanctuaries to meet kittens and find one whose personality fits best with their lifestyle. It's important that her parents go along, because they will be the 'responsible party' for caring for the kitten if/when your granddaughter isn't willing or able to herself. I personally think it's important that you choose a local shelter/sanctuary because then you'll be saving a life - there are SO many cats euthanized every day because they don't have homes. But I won't go on and on about that...
I don't mean to dissuade you from the kitten gift; I just wanted to share my little bit of experience with cat adoptions and perhaps it would be helpful to you! Good luck and I hope you have a wonderful holiday!