Story book graphic and character development

As a freelancer, I am looking to create a storybook with graphics and characters for an audience of 4-8 year olds. The style should be cartoonish and I am looking for help in developing 4-7 unique characters to bring the story to life. I am looking for creative and unique ideas to not only draw the characters, but also bring them to life and make a memorable storybook. I am open to different interpretations and ideas, so any help and insight would be appreciated.