You may want to try "The Giving Quilt: Fast Quilts for Comfort and Healing" Edited by Kathy Cueva and Susan Ziegler available at Joann's. I've used the patterns in it to make charity quilts. One of their patterns I sent to my niece (a first time quilter) who managed to finish a quilt in one weekend for her English class project. I gave her the info to add to her quilt label for copyright purposes.
Her teacher, her mom and I are delighted she could do it. If she can do it, your granddaughters can do it. Kristen didn't know how to sew before starting this project, but she's seen mom, grandma and I work on quilts for many years.