Can g6pd deficient kids under 5 take multi vitamin supplements? are all vitamins safe for such kids?

Standard types safe: The standard types of multi-vitamins or multi-vitamins plus minerals are as safe for children with G6PD deficiency as they are for non-G6PD-deficient children. If unusual, non-standard doses are used, then nobody really knows how safe or unsafe those supplements would be. Thus, one should stick with standard dosing and reputable brands.