What about Nature-Fil by Fairfield (50% cotton-50% bamboo rayon)?
I have not ever personally used it for 2 reasons: (1) I'm allergic to bamboo-rayon and (2) I only sell 100% cotton quilts because they are, imho, the best option for babies & kids. I've worked with Fairfield 100% low-loft Poly for quilted home dec items & with Hobb's Heirloom wool for a couple of wall hangings.
If you're not super concerned about your stitches really showing up, Soft & Crafty & Poly-Fil (both by Fairfield) both make good choices. They produce a very smooth quilt with very little loft to it. The one downside with polyester is that it is super lightweight so sometimes you need to either sew weights into the bottom of your quilt or you need to add a second hanging sleeve at the bottom so it hangs perfectly straight at all times. Of course, if you're not fussy about those kind of things, there are LOTS of quilters who happily make do without that.
By choosing a poly-rayon or poly-cotton blend, you get a bit more weight to help pull the quilt straight (gravity) and it does wash better with less risk of the batting getting lumpy or bunched up. Poly batting generally shifts more readily than cotton batting and can't be blocked flat as easily.
Wool is an option if you go with a dense (heavy) wool -- like people who get wool blankets at the Army/Navy Store to use as batting. I love Hobb's Heirloom wool & it definitely doesn't crinkle like cotton, but it has a high loft that is going to be puffier than low-loft poly batts. Wool batting provides excellent definition, but most standard packaged wool batting will be puffy around your stitching lines and, like poly, won't be heavy enough to hang absolutely, perfectly smooth.
It's a lovely pattern, though, and I really can't see you going "wrong" no matter what batting you choose. If it were my quilt, I'd either use Fairfield Cotton Classic (80/20 cotton-poly) or Hobb's Heirloom 100% wool with a bottom sleeve. If I wasn't allergic to rayon, I'd go with Nature-Fil but my poor little hands painfully swell and turn bright red within 10 minutes of working with rayon so it's not an option for me