Do any of your DCs get tummy trouble if they have too much yoghurt?
DD had a yoghurt a day from about 12 months (plus some cheese). She was fine. At 15 months I started giving her two yoghurts a day, because I weaned her and she won't drink cow's milk or formula. Since then (for about a month) she's had runny, horrible acid-smelling poo, although only once a day.
You keep reading about how good yoghurt is for digestion/how well-tolerated it is, but is there such a thing as too much? Yoghurt is pretty acidic...