Don't lower the guard. My two children at three were sleeping through the meetings...well ... they tried, but mom wouldn't allow it. But at some point the message began to get in their heads. Fast forward to many years later and my daughter gets baptized when she is 16. I always hope that now, at 21, she is mentally out, but it may just be wishful thinking.
My son is a different story. I pulled him out of the theocratic school, week meeting and preaching against his will when he was 11. I am quite confident he will never be a JW even though he has a soft spot for all the members.