A Christmas heirloom can be nothing bigger than a treasured ornament.
image by http://www.beckyrobinson.com/Kristina.jpg
It is often hard to tell what will end up being a family heirloom. Sometimes the items are priceless antiques, while others are simply treasured for their place in the family traditions. If you want to start a Christmas heirloom tradition--that is, designate an object as an heirloom that your children will eventually receive and should treasure and respect before passing it down--you will need to do some prep work to insure that the object is viewed in this light.
Make a big deal of unpacking the item each Christmas. When you get the item out of the bubble wrap, demonstrate a great deal of excitement and pleasure. This will help even young children realize that the item is important, and over time they will be excited to see it because you are.
Give the item a place of honor in the decorations. Place it somewhere where it can become a fixture in holiday memories. For example, if your heirloom is a china Christmas tree, then that tree should be displayed somewhere that it will be "visible" when your children recall their holidays from earlier years, such as on the mantle or in the center of the table as part of the centerpiece.
Refer to the item in terms of your children someday giving it to their children. Point out to your children that this item is special, and one day they'll pass it on to their children. This is the best way to make sure that it is viewed as an heirloom, because if they have heard for years that they'll get to pass a special item on, they are less likely to let it slip away.
Establish Christmas traditions around the item. Do the same things with the item every year. For example, you might all tell the story about how you got the item, or setting it up in its place of honor might become a family tradition.