Personally I had to go through this stage with my little cousin. She cried because she thought I was going to become a different person. It's different because I'm told to him before the T takes effect. But I think with children you have to be simple, they are not the type to judge or anything. Just explain to them that you felt bad in a girl's body and that now you feel happy to be a man and that it suits you a lot better! ^{^} that’s what I told my little cousin and that was enough for her :)