I name them instantly too. If they end up being boys, we don't change the name. The first chickens we ever had we hatched. Only two out of eight hatched and they both turned out to be boys. By the time we realized that one of them was a boy, she-ehem, he, responded to being called a girl. His name was BiancaCool
I name them straight off the bat and then if they turn out not to be the gender I thought/hoped they were I change the name XD