Hi Martina,
You may find this blog helpful. It contains a lot of links explaining benefits of different supplements for kids.
http://dsdaytoday.blogspot.com/2011/03/complete-protocol.htmlI'm researching this topic myself right now. I give my son only probiotics right now. I have been using several supplements for myself for years, so I'm a true believer in supplementation. I'm just like you, still unsure what to give to a small child. I tried to give my son lecithin to help his speech, and I believe it helped, although I did not stick with it, as he did not like the taste of it. I will probably start again as he is still not talking much.
Good luck!