Welcome, you are in for the ride of a lifetime
. You can skip the quilting of the appliqued blocks, this is up to you. Just remember quilting of a block is used to help hold batting in place (because in washing and drying sometimes the batting shifts and starts to bunch), I know you're using flannel as your batting it's still batting. Also when you applique all of the stitches will be rubbed from the back side during the washing and drying process (if this quilt is loved as we all want them to be, it will be washed and dried a lot), so the loose backing on the appliqued blocks will be able to rub freely. This will start to cause extra wear over time on your applique stitches. You might think about just a simple outline stitch around your applique or even a simple outline just inside of your block (either of these will help keep your backing from moving and rubbing). Good luck with your quilting and don't forget to show use your finished quilt.