I've worked with a few brands of acrylic (not my first choice, but sometimes required one way or another), and the stitch definition shown in the photo of the dragon hat may not be available in acrylic. The Lion's Brand cotton she suggests is fairly available (Joann's, for sure; don't know about others), so it may already be in your stash.
Otherwise, if stitch definition isn't important (and, for this project, it may not be), have at it!
DCM