For the best flavor, use ripe peaches that give just a little to the touch and smell like a peach. (So not rock hard peaches. Let them sit at room temperature for a few days until they hit that point if they are hard.)
You don't have to peel the peaches, though you could if you want to.
Increase or decrease the amount of peaches as desired. You can also just freeze a few leftover slices here or there to preserve uneaten pieces from kids meals.