I like your quilt very much with the straight edges. It suits the pattern. It will be easier to fold after washing and more for the baby to lay on if it is squared. And yes, scallops are much more tricky to finish. I don't particularly like corners and having four on a quilt is enough for me. To me, each indent of a scallop is a new corner, but not the same angle as an outside corner. If it were me, I would use all the colors in the blocks and make a straight multi-colored binding. It will be playful and fun.