I made a red work snowman quilt a few years ago using the Crabapple Hill Studio pattern. I followed their instructions which include a layer of muslin underneath the main fabric. Just needs large basing stitches after pressing the two layers together. I have made several of their patterns and they have all been prepped that way. I think it gives the embroidery piece more body, a nicer finish.
Before I started using Crabapple Hill designs, I did one by another designer who recommended an iron on stabilizer and that worked well, also, but I just prefer to not have the "glue" of the iron on. Hope you enjoy your project which ever method you choose! I'm sure your DGD will love it.