Are You Buying Us Presents?

The girls are nervous.  They pretend not to be, but they are worried.  A few weeks ago they bought us presents from their school's holiday shop.  They excitedly wrapped them and put them under the tree.
Several times since then they've asked, "Are you buying us presents?  There's nothing under the tree with our names.  You have presents.  Aren't we getting anything?"
We just laugh and say, "Santa will bring you presents so we don't have to."
They don't find this funny.
We find it quite entertaining.  First, we didn't plan to start this angst, but it works in our favor.  Whenever they are misbehaving we remind them that they don't have any presents under the tree yet.  Second, they waiver between "of course Mom and Dad are buying us presents aren't they?" and "when are you going to wrap our presents?"  For whatever reason they really have a lingering doubt that we're going to buy them presents.  It's interesting to listen to them try to explain the lack of presents.
Since Christmas is only a few days away, I suppose it's time to wrap their gifts and put them under the tree.  It's time to stop their angst and let them start trying to figure out what is in each box.