Hey, I just wanted to chime in about the whole "Santas" things at Epcot. I've done a lot of research on this while making my passports for the kidcot stations. Not all the countries have a "Santa" per say. For example, without giving too much away, here is an idea of what to expect:
Canada: the storyteller look a lot like our traditional Santa but they actually tell the story of Belsnickles which are little creatures that help Santa.
United Kingdom: tells the history of Christmas cards, Christmas carols, and mistletoe. They do have a Santa but it's basically the same tradition we have.
France: They have La Pere Noel, Father Christmas. Once again, it's pretty similar to the traditional American Santa and they just talk about other traditions.
Morocco: they have Ashoora. No form of a "Santa"
Japan: they have a vendor that is selling Daruma Dolls. No form of a "Santa".
American Adventure: they discuss Kwanzaa, Hanukkah, and you can meet & greet with a Traditional American Santa.
Italy: has La Befana, I won't tell you her story because it's one of my favorites but it's nothing like "Santa".
Germany: tells the story of the history of a Christmas tree. Only thing here is the parents "secretly" decorate it.
China: story of the Monkey King, once again, nothing like "Santa".
Norway: tells the story of Julenissen which is an elf. And then on Christmas day they have a tradition more similar to a different American holiday.
Mexico: is the story of the Three Kings.
I don't think your kids would really notice anything about the different "Santas" but if they start to question it, you could just tell them that Santa uses his magic to change himself to fit in for all the different countries beliefs...
Anyway, I hoped this help without ruining the surprise. Also, I obviously didn't put anything very eloquently but I was just trying not to give too much away.