While grain is important in making clothes, sometimes in quilting it is less so. When paper piecing the grain lines don't end up all going the same way. Sometimes getting the fabric pattersn straight is more important than perfect grain. If you starch your fabric well, you shouldn't have too much trouble sewing the squares together. The reason straight of grain is usually put along the edges is so the pieces stretch less when you sew them to the next square or row. Sometimes with solid coloured fabrics, the fabric looks a little different depending on the grain. This is supposed to be fun, so sew up your gift of love for the new baby.