This is just my thought - I really don't qualify as an expert.
When I do wall-hangings with raw edge applique, I do fuse it down and sometimes just straight stitch the edges. But if it's a usable quilt that will be put through the wash, I zig-zag or blanket stitch (with the machine) so the appliques will hold up through the washes.
That's a neat quilt and your GS will love it!