Just to add to Kong Yue's answer. If you want to search for things like 'childrens stories, you wouldn't search for 孩子故事, you would search for 儿童故事

在日常使用中，两个词的意思非常相近，都是指未成年人。只不过“儿童” 更为正式，孩子相对口语化。另外，当描述父母与子女之间的关系时，通常用“孩子”。 In daily using of chinese, the using of these two words are very similar, which both mean juveniles. But '儿童' is comparetively more formal. In addition, when we talk about the relationship between parents and children, we usually use '孩子'.

亲爱naomi !谢谢你！：）

besides,在中国12岁以下的孩子都称为“儿童”。