Have your kids ever seen a really scary movie? Maybe Godzilla, Frankenstein, The Mummy, Halloween, etc.
When you have a chance to talk with your kids without interference from Dad, ask them if they remember seeing the movie, and explain to them thay some prople can't tell that the movie isn't real. In the same sense, a few years ago YOU thought that the story of Armageddon was real, and for a long time you believe it was real, and you even made the mistake of teaching THEM it was real, but you've recently rea;ized that Armageddon was only a story, that it isn't real and is NEVER going to happen, that it was meant to SCARE people into going to church.
Anytime they even hint about Armageddon, remind them that it is just a story and isn't real. Reassure them that God (or Jesus) is LOVE and that people who are afraid of Armageddon have forgotten that god (or Jesus) is Love.
Basically what they need to do is de-program themselves to get rid of the scary pictures in their heads.