A number of years ago, I went to a children's book conference at the University of Mass. with some friends. We got to see Tomie Di Paola (StregaNona, etc.) speak about his Italian-Irish family and how he based many of his books on his upbringing in that culture.
He was very kind and encouraging and said that as long as you research your subject well, anyone should be able to write or illustrate any race or culture. He mentioned that he had created illustrations of white people and had always wanted to be very accurate in his portrayal! I was so grateful for that interchange and glad that I had had the chance to meet him!
Below is a great video by my favorite illustration teacher, Will Terry about diversity in children's books.