Our kids, Seth (age 7) and Emma (age 5), did the artwork for our Christmas card this year. I thought showcasing their own work was even more creative than a typical holiday photo. We've had rave reviews!
To do this yourself, simply scan the artwork and crop... Cut and paste onto a Word/Works page repeatedly and print on cardstock. Then, cut and attach as desired. I have used colored pencils, etc, to add a softer-than-marker look to their work before printing in the past, too. It's easy to mass produce when you use your pc!
This is a 2-D card and has a stamped greeting on the back where we signed it. These "1/3 page cards" fit perfectly in standard long envelopes and require no extra postage. They are easy on your cardstock supply, too, when you need to make lots of holiday cards! Grandmas love this stuff!