Good place for info on supplements/immunity boosters for kids??

[BABY_EINSTEIN'S_MOM]

Does anyone know of a good website/book to get some good info on supplements for better immunity? I used to supplement my kids ( the usual vit.C, echinachea, etc.) but haven't done it in quite some time. Now, with all of the H1N1 and seasonal stuff out there, I am looking into it again. Thanks