Those were not lies! Everyone is taking this question so personal and getting so defensive! I told my first born about Santa! I am guilty of doing this also! The question is not to condemn anyone but just make them think as it made me think about it. I don't know the answer which is why Im asking!
While this isn't exactly verbatim applicable here, I think we can extrapolate from this:
"
But whoever has doubts is condemned if they eat, because their eating is not from faith; and everything that does not come from faith is sin."
Food to us is a fairly minor issue, but under the Old Covenant there were a number of laws surrounding food and there was much conflict over that issue amongst believers during the early days of Christianity.
In the end we don't have to follow the old dietary laws under grace, however, IF we believe it's a sin to do something, it literally becomes a sin if we do it anyway.
Why? Because its the space your heart's in, you believe you've sinned against God and done it anyway, for whatever reason. (Never a good thing sinning against God, and never something we should feel comfortable doing)
There is a LOT of commercialization of the Christmas holiday, most of which I find utterly shocking as a believer simply because it's Christians engaging in it, but I have a fairly puritan mind too so there is that.
I do think such things as large spreads of baked goods and holiday decor and gift giving, Santa Clause etc seems to have taken the place, for many, of the Messiah.
But like food and eating, it's a heart thing... it doesn't have to take the place of Christ, in which case the celebration wouldn't run afoul of idolatry commands...
You can make anything an idol simply by giving it the place in your heart that Christ belongs. You can make an idol out of following laws just as much as you can make an idol out of Christmas celebrations...
It's really about where your heart is. I would caution you though, not to celebrate at all until you work through what is sin and what isn't where concerns this matter.
Is giving to the poor ever a bad thing? No. Is decorating your home a bad thing? No. Is memorializing the birth of Christ a bad thing? No, even though it's not commanded. Is getting together with family and loved ones a bad thing? No..
So what is left is the question 'are you, personally, making this holiday into an idol, giving it the place in your heart where only God belongs'? Or 'should God have a higher place on this day than I'm currently giving Him'?
If you want, have a Christmas without any commercialization of it... see where your heart is - your kids might not like it, but it might do all of you good to explore this topic together. Have them look up Bible verses in support of their positions, as well as others that don't support them and so forth... discuss it as a family, go through it as a family.
That might just take you all somewhere really good, if your kids are old enough...