Fat-soluble A, D, E and K: all are important to have, but can be toxic if taken in too large quantities.
Water-soluble B group: Thiamine, Pyridoxine, Riboflavin and Niacin and a few others; all readily available in fruit and vegetables, but can be deficient especially where antacids are used long term.
Vit C: Often taken in large doses to dampen viral infections, without any evidence and fortunately seldom seen on SCURVY in true Vitamin C deficiency.
Multivitamins: Can be useful, but more focused supplements, using specific elements lacking in a child’s diet like Iron, Zinc, B12, etc. should be discussed with your healthcare helpers.