Whatever we say we say to everyone. It doesn't matter what is his age. Krishna Consciousness teaching does not depend on the age. It is the eternal platform of the soul. This is the meaning of transcendental; that is beyond any consideration of material qualifications such as age or intelligence. Just like thunder in the sky does not need any explanation to any old person or to a young child, similarly, the transcendental sound vibration of Hare Krishna and preaching of Bhagavad-gita philosophy will act on everyone, regardless of whether or not they are understanding at first.
Letter to Prahladananda, 5 October, 1969