Yep, you will need a pigma pen and send it to each person, which can be expensive. Otherwise, they will use ballpoint or some other kind that either runs or washes out. Enclosed a note telling them they must use the pen and stay within the freezer paper! When you get them back, heat set the sginatures with an iron.
For one signature quilt I made, I cut out 3.5" squares, ironed 3" squares of freezer paper to the backs (gives them a clear area in which to write as well as stability for writing), and took them to the rehearsal dinner. After the wedding, I put them together and gave them the quilt later. (Now they are divorcing, but that's a different story!)
I prewash most of the fabric I use in quilts. Just put it in the laundry with my clothes, iron, and keep on hand to use. If you want to avoid raveling edges, just pink the ends, snip off the corners, or run a serging stitch along both ends. I don't bother - just cut off the ravels after it's dry.