To learn about the Suzuki Method and Philosophy, please read Nurtured By Love by Dr. Suzuki. There are many other books that your teacher can recommend as well such as To Learn With Love by William and Constance Starr.
The child should be immersed with the music right from day one or even before. As long as the ear can hear it, the child will be able to reproduce it on the piano. Play the recordings every chance possible.
Your child will learn to read music as soon as they are ready. Usually, I like to start at the end of Senior Kindergarten for those students who started lessons at age 4. Later beginners may start reading earlier since they will be reading at school as well.