Give them an alternative that is appealing and rooted in common-sense. Ask them gentle questions. Offer alternative points of view.
E.g.
You to your 5 year old: "Tell me about Noah and the animals son?"
5yo: "Two by two ... built a big boat ... bad people ... etc."
You: "That's great! Then what happened?"
5yo: "Jehovah saved them because they loved him!"
You: "What about all the people and animals who didn't get in. What happened to them?"
5yo: "They all died because they didn't love Jehovah!"
You: "What they all drowned?!"
5yo: "Yes!"
You: "That sounds awful! I'd never kill anyone because they didn't love me. Perhaps some of it is just a story? Anyway, shall we go and get a McDonalds?"
Or ... once a month during summer ...
You to the whole family: "I'm going to the beach/lake/picnic on Sunday, who's coming with me?"
Family: "We've got the meeting."
You: "Well I'd love you to come to the beach - we can have fun together!"
Wife: "Our meetings are important."
You: "And so is family time so I'm going to the beach with the kids. If you want to take the baby to the meeting you can make other arrangements, I don't mind it's up to you."
Little bits here and there. Little and often, little and often.