Nobody has said a child is anything other than an innocent civilian. However, you have to remember that Hamas and the childrens' brainwashed parents are using them as human shields. I don't think you appreciate the power of the cult of martyrdom in their culture. They even have Palestinian kids' TV shows, with a mickey mouse character brainwashing the kids to think it's cool and trendy to want to grow up to be a martyr and kill Jews.
The Israelis are not just attacking Hamas while they're at home eating hummus; they are attacking Hamas while Hamas are continuously firing rockets at Israeli civilian areas. Now, do you seriously think the Israelis should sit back and let Hamas keep firing these rockets into Israel, because they've got human shields around them? It's a nice idea but how else do you propose to stop Hamas firing the rockets? Ask them nicely?