I know at times it can be frustrating. But, as a professional probably I could have gave her the option to choose: 1 the craft is not age appropriate (and your role as educator is to make sure every child is able to participate and support the craft activity with any little skills they have); 2 how ever it can get done but not as the picture in the box. Using al the pieces as a loose parts and regular glue for everyone and when everyone is able to participate. 3 for the grand parents to see, you can send a digital picture of the grand child hands on. Or last, the mother and the child can do it together. (As you stated before) but not just you doing it alone and on your own afternoon prep. time. I'm sure the grand parents will love to see their grand child working on it. Not just and the end product.