Your quilt top is absolutely BEAUTIFUL!
Whatever you decide to use, TEST IT ON SCRAPS FIRST! I learned this lesson the hard way--there's an almost done small quilt in my closet that I CANNOT get the marks out of even though I used a "washout fabric marker". (Luckily my disaster quilt wasn't nearly as nice as your quilt top!)
I have had good luck with the blue wash out fabric markers and the heat removeable pounce chalk...