Polyester batting doesn't shrink, whereas cotton batting does. You don't get as much crinkling with polyester batting, but you still get a nice soft-looking result. Definitely try it to see what it looks like.
I remember the very first quilt I made. Pre-washed all the fabric, hand quilted it, and used all-cotton batting. It crinkled so much I took it to a quilt shop to ask if I had done something wrong! Nope. That is the way cotton batting acts.