Quilting fabric for a backpack
I'm making a backpack for my granddaughter. We found a pattern that she likes, but she wants the outside fabric to be quilted. I'm planning on using a very thin batting, and I have a couple of questions:
(1) I have both Quilters Dream Poly and Quilters Dream Cotton, both "Request," which is their thinnest type. Is there some benefit to choosing poly or cotton here?
(2) I will be preparing the outer fabric by quilting it first, before I make the backpack. Would there be a reason to back that fabric with muslin as well, or should I just use the outer fabric and batting? Will the quilting definition look different if there is muslin included as backing, or will it just add another layer that will make it more difficult to assemble the backpack?
Thanks!
Carol