Of course, it's best to not lie in the first place. It's better to not start the commercialized-marketing-extravaganza-masked-as-tradition in the first place. Then you will have no problem having to explain it later.
If you are religious, you can celebrate Christmas as the birth of Christ. The gift giving is more of spreading joy to others (not expecting something for one's self).
If you are not religious, you wouldn't believe in Santa anyway, and Christmas is just a holiday you can spend time with family.