The best option is normal organic yogurt with some fruit puree. Oh, unless you think your DS2 may have a problem with milk protein, I think they denature it a bit for the Hipp yogurts. But if he's already on dairy (and maybe even if he isn't), plain yogurt with fruit puree is much nicer than any 'baby' yogurts.
I give my DS natural yogurt, or natural greek yogurt, then i add fruit puree to it have been doing this since he was 6months and he is now 18months and still loves his yogurt.
but i try not to give the non or low fat varieties as i think he probably needs the fats particularly as he drinks semi-skimmed milk. Tried to give whole fat but he wouldn't drink it, so i figure that the yogurt helps to balance this.