There are several places to look for the best royalty - free children's stories. One great source is Wikimedia Commons. While it's mainly known for images, it also has some free - to - use stories. Additionally, some independent authors on platforms like Smashwords might offer their children's stories for free or under royalty - free licenses. You just need to search specifically for those terms. Also, your local library might have some e - book collections of old, out - of - copyright children's stories that you can digitize for personal use as long as it's within the bounds of fair use.
You can try websites like Project Gutenberg. It has a vast collection of classic stories that are in the public domain, which means they are royalty - free. Another option is Storynory, which offers a good number of free audio stories for children that can be used for various purposes without having to worry about royalties.