Wow, that is truly beautiful! Nothing to be ashamed of in that piecework! As for the quilting, I'd say lighter or darker brown thread (variegated?) lines as if to show "planks". Blue, green or white on the water for wave shapes and white in the sky in cloud shapes. You are doing all the work, don't be afraid to show off the design a little! And don't forget to put the story on your label for the back, it's a story that will be cherished through generations!
Just went back and looked at your work. Any design you add to it will be perfect! And I love that you want to hand quilt. Maybe I'll try that in my next life!