I know this struggle. One of the things I have had to deal with is that my child goes to school, so if I do not inform the other children inform. I would prefer that my child has my values and a chance to process before getting some other values or the shock through other lenses. We also do not watch the news. I made sure my kiddo never saw the footage of the planes or the twin towers for as long as I could. (She was much younger at that time.) However when she was a bit older we visited Ground Zero and she learned about what happened in a more real way. She has seemed able to handle a "real" experience better than some abstract discussion. She learned about the Holocaust through the Holocaust Museum.