The top-stitching is decorative, tho it really adds a lot! Perhaps practice with a scrap piece of fabric that you trace the stitching lines onto, to see how well it turns out? But to answer your question, the facing shouldn’t flip out if you do the edge-stitching where you stitch the neckline & facing seam allowances to the facing (I can’t remember which step this is, but it’s right after you sew the facing to the neckline). So you could leave the top-stitching off if you wanted to. The same with the pockets – stitching them to the dress front isn’t required and for a dressy version you might not want to as it does give a more casual look. But it keeps the pocket bags from flipping to the back, so it’s something to consider. Either way, I’m sure your playtime dress will turn out well!