How wonderful and how exciting! I must admit that in my life, I can only equate your situation with teaching my DD to cook (she absolutely hates anything to do with sewing and refuses to do anything more than 'maybe' sewing on a button) A lot of her childhood friends had Easy Bake ovens. DD learned by using real utensils, real recipes and a real oven. And not to blow my own horn, but she is an amazing cook and surpassed her Mum many years ago.
I also agree that your DGD is a little too young for a real rotary cutter. I would start with simple kits (even ones you make up for her instead of investing in precuts) like a pillowcase, squares to make a dolly blanket, precut sleep pants, etc.
Oh you are going to have so much fun!!