Oh my gosh! How fun for your family and what a great surprise! So many great suggestions on how to surprise your kiddos with it!
We are planning something similar in that we are surprising our kids with a WDW trip that same week before Christmas, too! Our kids are older, (11 & 13), but we do a “Surprise” Christmas Adventure every year. We don’t tell the kids what we are doing or where we are going for the trip. Instead I give them a “clue” just before we head off for each stop of the adventure. Then when we are done with each fun stop they get a clue for the next one. It’s kind of like the Amazing Race, but with fun stops and a slower pace!
Thought I would share in case it is something your family would enjoy as well! Our kids love it and look forward to it every year! Have a magical Disney Christmas Adventure!