In addition to trying a shorter and more closely fitting top (which is true), I just wanted to say that skirts do not work for me at all as a MOTG wear as well, precisely from the same reason (bending, picking, climbing the jungle gym - all these activities cannot be done in a skirt while keeping my underwear covered). I decided to stick to clamdiggers and tunics with leggings. So I only wear skirts to work. But! as Khris said, skirts can work with leggings too, so you might want to try that.