My parents constantly preach vegan-ism, Christianity and a whole lot more!?

You have to think carefully and need to talk to your parents about this matter. Tell them you are not pressuring your children to eat meat. It is their choice if they want to eat meat or not. Let the children decide if they want to eat meat or not. By showing those thing we are conveying wrong message to the children. For example I am vegetarian and I don,t eat meat, fish or eggs but my children and my husband are non-veg. But I don,t allow my children to eat pork and beef because of religon matter. My youngest son (age 4) is used to vegetarian but now he eats meat and this is choice. You need to speak in good tone with your parents that let the children decide what they want to eat. You have to talk to chidren in calm voice and explain about veg and non-veg food. You tell your parents if they keep preaching about non-veg food, you need to tell them to stay away about their family matter it is destroying their family.