No special dress code for children. A 12 year old boy can wear anything like shorts and T-shirts. Even for girls, who are younger than 12 and do not look like a teenager, can go without Islamic cover. If you are on package tour and do not need to walk around, even girls can wear short pants and T-shirts. But if you are going to walk around or traveling by bus or train, girls should wear pants and long sleeves not to draw locals’ attention.