As far as I am aware, you square up after you quilt, as the quilting itself can distort the fabric. The quilting doesn't unravel unless you leave a cut edge for a longer period of time, or handle it a lot. If you want, you could square up the quilt, and then go all around the outside edge with a straight stitch, just to anchor the edges together before attaching the binding. Then, bind with a 2.5in wide strip, folded in half, with a 1/4in seam.