Children should be taught to write thank you cards at a young age. If they are very young then the mom can write them for the child. As the child grows older, they can write together. By the time they are teenagers, children should feel comfortable enough to write them all by themselves. Make this one of your goals to do with your children for Christmas. Reinforce this again by writing more of them when it’s their birthday next year. After that, they should be comfortable and confident enough to write their own cards for any occasion. Maybe they’ll even remember to write you one.