Never too soon for the magic of Science
If you are a parent looking for ideas, here's a collection of science books for kids from Dover. It's never too soon to start exposure to Physics and Science. The sooner the better.
And here is an updated list of the "50 Best Science Books for Kids" from "PsySci.co"
For further real life inspiration on the value of early introduction to science, have a look at the early life of the renowned physicist Richard Feynman. He had a powerful relationship with his father in this regard. Young Richard not only benefited greatly from his father's mentoring, he even payed it forward by encouraging his younger sister to realize her goal to become an Astrophysicist despite discouragement from the other role models in her life.