Nimitz Library has a very small (and dated) selection of print juvenile literature.
One strategy would be to search for individual titles in the catalog. (Only those affiliated with USNA will be able to access online titles.)
DoD-affiliated individuals will find resources for every age and school level at the DoD MWR Digital Library, look for the Children's Corner. (Note that a card reader is not needed; one needs only to enter information from your card, as directed).