I have started my DS with plain unsweetened yoghurt........he quite likes it and seems to be fine with eating it, I wouldn't start giving the sweetened ones jut yet....too much sugar I would think
Maybe try the plain stuff and see how that goes.........the extra calcium is good for them as well, especially if you don;t want to buy a follow on formula (assuming your feeding formula)
Let us know!!
Also, ask your DR and see what they say, I knwo they can often give empty answers but it's worth asking!