Final answer:
Complimentary children's DVDs can usually be found at the library, where they can be borrowed for free.
Step-by-step explanation:
The best place to find complimentary children's DVDs would be at the library. Libraries often carry a wide selection of DVDs, which include children's movies and educational content. Moreover, libraries generally allow you to borrow these DVDs for free with a valid library card. While other options like a toy store, movie theater, or grocery store might offer DVDs for purchase, they typically do not provide them for free.