Jeanette, I bet you will be much happier with the quilting if you go ahead and add strips to the backing edges to give you something to hold onto while quilting. I would think at least 4 additional inches per side for hand or domestic machine quilting, and 6 inches for long arm quilting.
Whether you are doing the quilting or are sending it out, the quality of the quilting suffers when there is not enough edge fabric. Ask me how I know.
I love your colors, so cheerful! They really do justice to the design.
Barb in Alabama