Easy Christmas songs?

My son has been playing for one week now and is actually doing pretty well.  He can play "Boil Them Cabbage Down"  which may not seem like much but he hasn't had any musical training.  Unfortunately, I'm not much help as the more I learn about the MD the more I find it is unlike the trumpet that I played for so many years.  All that to request some suggestions, and tabs, for easy Christmas tunes.  They are requesting special music for a Christmas service at church and he was thinking about seeing if he could do a song or two.  His instrument is tuned DAA.