The child would have the text in front of them, potentially, as the audio gets played. But I can’t know all use cases. Each parent or educator might have the opportunity to use the audio as seen fit.
Perhaps the reverse needs to be asked though.
What downsides can you foresee of having the entire series recorded as audio? What possible damage could ensue?
Yes, the audio is free and open source and is available on the Internet Archive through LibriVox, as is the text.
Worst case?
They still can't read but are able to rattle off the entire series verbatum.