All of your options are good ones, so there appear to be no 'right or wrong' answers! Both size quilts are nice, but if your quilt is for a child to hug and drag around, the smaller size is probably best. The dark bubble fabric goes great with the rest of the fabrics, so whether or not you add another round or not, it would be great as binding and backing in MHO! Great colors too since they won't show dirt easily if on the floor a lot.