The Christmas tree: believed to have begun in Germany in the 16th century. Martin Luther is credited for starting the tradition on lighting a Christmas tree. He had been walking home one winter night and was enthralled by the sight of the stars twinkling among the evergreens. When he arrived home, he wired several lit candles through an evergreen to show his family how it looked. Candles have since been replaced with electric lights. German immigrants brought the Christmas tree to America in the 1830s.
Santa Claus: due to the long and varied history, I will simply provide a link to a child-friendly history of Santa: North Pole Santa Claus
Candy Canes: dates back to 1670 when a German choirmaster bent sugar-stick candy into a cane shape in an attempt to emulate a shepherd's hook. The first candy canes were all white and were given to the children to keep them quiet during the long church sermons. The first historical reference to candy canes in America is in 1847, when a German immigrant decorated his home with candy canes. It was around 1900 that stripes and peppermint and wintergreen flavors were added to the candy canes. While there is a lovely story relating the history of the candy cane to the Bible, there is actually no historical proof to back it up, quite the opposite in fact. Personally, if it helps remind someone of the reason why we celebrate Christmas, go ahead and tell it, just know that it is not the real story behind the candy cane.
Star or Angel on Tree Top: represents either the Star of Bethlehem from the Christmas story in the Bible or the angel that told the shepherd's of Christ's birth. The Christmas story can be found in the Bible in both the books of Matthew and Luke (Matthew 1:18-25; Matthew 2:1-12; Luke 1:26-38; Luke 2:1-20). The Christmas story that is usually told is a compilation of both of the accounts.
While there are many more emblems of Christmas, for this age, I am only going to teach these. There is also a deeper history behind Christmas itself, particularly why it is in December, but at this age, it is too deep a subject to cover.