Hi Barbara!
Sounds like fun- one time we surprised our kids by telling them we going for a ride to look at Christmas lights & decorations....8 hours later, we were looking at them in Disney!
My husband and I also recently surprised our kids with a Disney cruise and struggled with this very idea!
We finally settled on a scavenger hunt! We started off my giving the
kids a treasure map that lead them to a clue. That clue lead them on a
hunt all over the yard for more clues. Finally, they "discovered"
treasure under a tree in the backyard. In that spot was a picture of the
Disney cruise ship with the date's we were sailing. They had a fun time
with the hunt, and still talk about it today!
Another idea I have, if you're counting down to Christmas, would make
your own Advent Calendar. Perhaps you can pick up a fairly inexpensive
one at a local store and "tamper" with it a bit -- adding in your own
Disney bits on the night before you leave.
For more suggestions check out my fellow Disney Moms Beth's
ideas or Kimberley's
ideas here.
Hope this helps! Have fun surprising them!