I think it's official my best friend and I have gone totally bonkers 
A few years ago I read on here about the Elves hamper Christmas Eve and as my friend visits with her DCs for the afternoon to do our presents and her DD1s birthday (it's Boxing Day) I asked her if she minded me doing letters from elves with hot chocolate and DVD for children. It was secretly placed outside front door which we arranged to be knocked.
The DCs LOVED it and so we continued the trend over the years. They have had new blankets and DVD, new pjs and letter, new dressing gowns and letter and last year we all got a letter (even the mums!) with a ticket each to see frozen that evening. The DCs found our letters hilarious as we put things like trying to be more patient with DCs - they were at age of asserting independence!
This year we have lost the plot - I swear it!
We decided again to 'do' something with DCs and after much thought and research of activities decided to visit a fairly local ski slope for ringos and they have an adventure park there.
So I wrote a poem to send the DCs through the post (we just hang it through letter box!) with a reference to needing warm clothes, mums have a map and further letters to be placed inside. So the events would be revealed as the day went on.
My friend jokingly laughed about messaging it!
So we have actually set up an email address registered as Elf North-Pole and saved lots of emails as drafts ready to send each child at a given time. We are also going to change mail ringtone to the sparkly sound to surprise them when it comes through. (They have simple bings ATM). This has involved me registering earnie elfs email as an email on my iPhone!
We have jokingly called it a 21st century Christmas!
(Before anyone goes on about cost on top of Xmas we aren't extravagant with our DCs and it's costing £9 per child for the ringos and adventure park)
Please tell me that you have all done bonkers things all in aid of the magic of Christmas 