Your sashings would not "have" to be the same width, and that could give you extra width or length that you need. Or, I like the idea of adding and extra plain block with the name and birth data embroidered on it. I did that for my grandson's shawl. We didn't know the sex before, but I knew the names chosen and I knew the month and year, so I worked it out in cross-stitch, and was ready to "go" as soon as the birth. All I had to do was fill in his name and the date. Had it ready to bring him home in!!