I have two City Weekend charm packs that I'd like to make into a small quilt for my daughter. I plan to machine wash them cold and line dry -- do I need to prewash? I worry about the wee squares fraying away (although they're pinked already). Is there much shrinkage or color loss with these fabrics? I had no color bleeding and only a modest amount of shrinkage with the interlock, though I was expecting more. Cut am 18m Sailboat top from 1 yard and had loads left over.