I have done 3 of these so far and have the blocks ready for another one for a wedding in October. I found that making the blocks first really helps keep folks from writing in the seam allowance. I also took a block to Hobby Lobby and had them make a picture mat for the block, going into the block 1/2" all the way around to preserve my seam allowance. I ironed freezer paper to the back of the blocks and taped the block into the mat. Worked great - you can see the finished quilt here:
http://farmquilter.blogspot.com/2015...-quilting.html
One thing, you do not want to quilt over the written words, so be mindful of how large a space you leave for the signatures. The blocks I made for the October wedding are here:
http://farmquilter.blogspot.com/2015...y-goal_31.html I really like that pattern - easy to do in the bride's colors and the area for signing is large enough without being too big for no quilting besides SID.