I have used minky for backing quilts several times and have had very good luck with it. I find that the quilting kind of disappears into the minky. I think when you do your practice piece you will be able to decide on the quilting you want to use. I don't think it will need anything elaborate since the texture of the quilt will be wonderful. I normally use Quilters Dream batting. They have a thin version called Request, I think. Check their website for particulars. You have made an awesome quilt and I'm sure the girlfriend will love it! BTW, I do my quilting on my DSM. It sounds like you may have a long arm and so your experience may be different than mine. I hope not!