I would treat it very much like a sex talk. Make sure it is age-appropriate and at a level the child will understand. You can also say, "What do you think?" and then respond to their answer. If the child has any fears, you can deal with those.
"Don't worry, Jehovah is perfectly just and perfectly loving. Jehovah knows my heart and will take care of me."
"If you didn't have to go to one meeting, what would you want to do?"