If I were to put one in I would wait until 2 wks at a minimum. You wouldn't want it at 1 day I wouldn't think. They are still trying to figure out where and what food is. You wouldn't want to risk craw impaction if they were to gorge on it. I don't put one in at all.
Play Sand is good, but i use the same dirt that the big girls use to dust themselves in, i figure if its good enough for them then then it will work for the chicks too.
I try to get clean dirt from the same area.