The Bodhi Tree, under which the Buddha attained enlightenment, is a species of banyan fig known as "sacred fig" (ficus religiosa, of 'bo' tree). One might purchase a potted live ficus tree (a ficus benjamina will suffice if a ficus religiousa cannot be found) decorate this tree with lights, strings of beads representing the interconnection of all things, and three shiny bulbs representing the three jewels of Buddhism. A statue of a meditating Buddha may be placed at the base of the tree. A star on top may represent the "morning star" viewed by the Buddha at the moment of enlightenment.
One may also consider to build a more elaborate scene, such as this created by a Buddhist temple in Hawaii:
Make, with your children, your own decorations for the Bodhi tree and around the house. Cut out and decorate paper Bodhi leaves to hang around the house. Cut out paper stars to color and decorate with your children and hang around the house, representing the morning star Buddha saw on the morning of his enlightenment. Help your children make his/her own Buddha to be placed under your Bodhi tree, such as shown and discussed HERE:
Place images of Buddha in your windows and outside your hime. String multicolored lights around your home, representing enlightenment, the various colors representing enlightenments forms and paths.Turn on the lights each evening starting on December 8 and for 30 days after.