Concerning seam allowances -- for Linus quilts with simple patterns made with squares, such as 4 patches, I always use a 1/2" seam. I know it is not conventional, but I think a wider seam allowance is a good thing is children's quilts. It makes no difference for the patterns I use (making the blocks fit ok), and it sure does give a little more "wiggle room" if you are working with squares cut by amateurs.
Dayle