John was an elderly man and their leader. He used this expression to show his love for them. See how you translated this in [1 John 2:1](../02/01.md). Alternate translation: "You who are as dear to me as my own children, do not let" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "lead you astray" is a metaphor for persuading someone to believe something that is not true. Alternate translation: "do not let anyone fool you" or "do not let anyone deceive you" (See: [[rc://en/ta/man/translate/figs-metaphor]])