That's an interesting use case! Where does Alexa gets its bedtime stories? Does it read from public domain storybooks or must you purchase them like audio books?
It's an official-branded skill, "Amazon STorytime" that is a built-in for Alexa, e.g. you can invoke it by saying something informal, such as "Tell me a bedtime story" or "Tell me a story", rather than the way other skills are more narrowly namespaced.
It says the app "contains curated stories from the Amazon Rapids app library as well as a selection of Audible short stories". It's pretty good, as it features actors and sound effects. Can't say any of the stories were interesting to me (was hoping for Aesop Fables type stories, which is about all I remember growing up myself).