Many new writers believe that writing for children should be easier than writing for adults, but actually the opposite is true! You have to decide what age range you'll be writing for and write in a way they can understand, engage with your characters AND have fun. It's not about talking down to them or giving them a hard moral lesson (though most stories for children tend to have some form of learning or life-lesson, it just has to be subtle!)

Children's books tend to be much shorter than adult books, especially for very young readers which are far more picture-based than text-based. So it's important to stick to the point, choose every word wisely, have one theme, not lots of side plots, and make the ideas fun and exciting. 

Below is a chart showing an overview of appropriate word counts for the different age ranges and types of books you can write for. This is a guide only, the ranges can vary or crossover depending on where you search but it's useful to have an idea what to aim for. These ranges work for both fiction and non-fiction.