If you want to write children's stories in rhyme I've published a post on Hubpages which gives you a few ideas - http://johnnyparker.hubpages.com/hub/Writing-in-rhyme-for-childrens-picture-books
The story for The Lazy Seagull was written in rhyme because I think it adds extra interest to the story and helps the narrative to flow. Kids like words that have a sing song quality. Plus I like rhyme and I get a buzz out of making it work. It's not as difficult as you might think and there are online dictionaries which will find a rhyme for you. Job done!