Let me pre-empt this with I have one of those children that people generally give a wide berth to. He's full on. All. The. Time. He is hard work. But that's how he is. He does make life interesting though lol.

A bit selfish here, but I love Christmas, and I love everything about it, so I would never use that as a threat as I would miss out on the magic. Santa will come. Always. Until they have children of their own. Just like he did for me.
We use our elf like a "Where's Wally". It's a bit of fun.

However, if my child had the presumption and bullish audacity to say something like that, then perhaps I would postpone Christmas or some parts of it. I don't want to raise my children to just expect things because everyone else does. I would think maybe that was a reflection of us and our parenting and perhaps something needed to change.