My quilt is 68" by 68" comprised of 4" squares...how big should I make my border?

I've made a quilt from my son's baby clothes that is 68" by 68". I was thinking about skipping a border but many of my friends think I should add one. I'm wondering what size border would be appropriate and also should I do a double border or just one color? Seeking some "professional" input. Thanks!!