I find writing for young people very difficult. I can write for young adults, but no younger than that. I have found a very helpful tip though. First you need to imagine yourself back when you were a child and think about things such as what was important to you at that age, challenges you faced and where you enjoying going on day trips. Then you write a starter paragraph and once you have finished, you go back through that paragraph and underline the words you didn’t know at that age. You’ll be surprised by how many you use!