|I sew a lot for my kids, and they (and my husband) need help telling the front from the back. For an unembellished PJ top or bottom, this can be difficult for the "unenlightened". If I have it, I use a woven size label, but sometimes I don't have one, or it isn't the right size, or will show through the fabric.
If you have a scrap of grosgrain ribbon or twill tape, double it over and include it when the neckline or waistband is finished, just like RTW. For kids who are "fussy" about scratchy tags, I LOVE scraps of rayon seam binding, which are SOFT. You can even write on the tab with a permanent marker.
You can also use this tip to keep sets together, for instance tops and bottoms with the same color tabs, if you make multiples in different size ranges for different kids