Hi Olga!
Thank you for your questions and you're welcome to keep asking as many questions as you want!
I love visiting WDW in December but its a tricky time weatherwise!
While on vacation at WDW during December I had to wear mittens in the evenings. A few years later I walked around in short pants and a light shirt while looking at Christmas decorations. So even though it can get pretty cold during December at WDW, the weather could also be warm enough for some water ride fun. A little detail I have noticed about water rides, such as
Splash Mountain, is that during the winter, for some magical reason guests don't come out as wet as they would during the warmer months.
If I'm not mistaken, moon cakes are delicious Chinese pastries. Even though I've never seen these at WDW, I have heard they're available at Epcot, usually during the months of September and October.
Have a magical time!