Here are some ideas to inspire:
For the younger children are a couple of simple ideas on the CreativeFabrica website. A 3D Christmas tree unfolding card made from a simple card rectangle and three pieces of Christmas tree. Their second idea is a pop-up front saying Season’s greetings, or more likely Happy/Merry Christmas. Both of these ideas could spark the children’s imaginations and they could use these methods to make their cards with Christmas baubles, gingerbread men, Father Christmas, reindeer, robins, etc.
A slightly more difficult one is the 3D house in silver, more suited to slightly older pupils.
The RedTedArt site has another lovely idea using three Christmas Tree cutouts, still joined at the one edge, each folded lengthways to make a simple pop out when the card is opened. Again, this idea can be used for almost any Christmas symbol.
The Paper Crafter has a couple of really stunning ideas but they are not for the faint-hearted, however again there are a couple of easy ones that may inspire. I really like the simple Father Christmas pop up and the child’s art will be behind Santa! It makes it much more personal.
3D Christmas Cards combine both art and D&T, they are both thrilling for children to make and families to receive.