Need advice on taking care of biracial hair?

I need advice on taking care of biracial (black/white) son’s hair. I have tried different things people have suggested to me, lotion, Redken anti-snap, but his hair still looks dry and frizzy. His hair isn’t very long but he is only 3 so it’s a struggle in its self to get him to let me comb it. I saw online that it was best if I only washed it once or twice a week. Is that right? I’m trying that but I can’t tell a difference. Also any suggestions for good children’s shampoos and conditioners would be greatly appreciated. Thanks.