At 8 years old they are old enough to be logical, I would think.

Explain that there really was a Saint Nicholas many many years ago, and Santa Claus was an extension of that idea for younger children to be made happier by the thought of Christmas gifts being brought by Santa.

Tell them that it is a beautiful thought for family members to share gifts with each other, and that doing for other less fortunate people is important, too.

Suggest that they help you buy or make small gifts for children who are too poor to get presents, or older people in nursing homes, or patients in hospitals; and have them go with you to give out those gifts so they can see how appreciative the recipients are.

Tell them that they can now be Santa to other people.

Hopefully all the above will make them feel better, and explain that this type of activity will put the real spirit of Christmas to work.

It should be explained that Santa are those people who are generous usually on Christmas day. That Santa is just a name used for these people. And tell him about he can also become a Santa even at his young age by giving to indigent people.

It should be stressed that generosity is being Santa. Here are some articles that could help you.

http://www.ehow.com/how_2085690_explain-santa-claus-child.html

http://www.howtodothings.com/religion-spirituality/how-to-explain-santa-claus-to-your-kids

Good luck and happy holidays in advance.

Is there really a Santa Claus? Today, Santa Claus still brings toys and gifts to good little boys and girls around the world. Sometimes children have doubts about Santa Claus and wonder if he is real.Yes, Virginia, There is a Santa Claus Originally published in The New York Sun in 1897. We take pleasure in answering thus prominently the communication below, expressing at the same time our great gratification that its faithful author is numbered among the friends of The Sun: Dear Editor: I am 8 years old. Some of my little friends say there is no Santa Claus. Papa says, "If you see it in The Sun, it's so." Please tell me the truth, is there a Santa Claus? Signed Virginia O'Hanlon The answer as published in the New York Sun was: Virginia, your little friends are wrong. They have been affected by the skepticism of a skeptical age. They do not believe except they see. They think that nothing can be which is not comprehensible by their little minds. All minds, Virginia, whether they be men's or children's, are little. In this great universe of ours, man is a mere insect, an ant, in his intellect as compared with the boundless world about him, as measured by the intelligence capable of grasping the whole of truth and knowledge. Yes, Virginia, there is a Santa Claus.

tell them there is no easter bunny or tooth fairy either