Pre-washing is a good idea, as is smaller stitches. If you still feel somewhat paranoid about it coming apart, then sew a narrow zigzag outside the 1/4" inch seam after you have sewn the 1/4" seam. Then, the zig-zag will have to come out before the 1/4 inch seam can be pulled apart from fraying.
That is a lot of work, though.