Super cute quilt top! I would pick a busy print for the back if you plan to quilt it yourself. Busy prints hide any little bobbles in the quilting. The other thing you want to consider is what color thread you or your LA-er will use to quilt it so that it coordinates with the thread (although that isn't quite as important with playful children's quilts). Personally, I think quilters' cotton is plenty soft once it's washed a few times & it's easier to quilt than flannel, but I've done both. One other thing that affects how cuddly a quilt is is the batting. For kids' quilts I only use cotton, but I switched to a high loft cotton (Warm & Plush) to make it snugglier. If you do go with flannel, wash/dry it the way it will be laundered when completed and also to really make sure to baste it well so it doesn't shift while quilting.