Hi, Hilary! Best wishes on your upcoming wedding, and congratulations on your choice of spending your honeymoon at Walt Disney World!
Unfortunately, there really is no definitive answer for your question. You see, the Holiday Services Team and the Lighting Engineers and Technicians begin preparing the parks and resorts for Christmas as soon as Halloween is over. However, it takes several weeks for the complete transformation to take place. Since your honeymoon will fall only a week after Halloween, my guess is that not everything will be up and ready for Christmas by the time you two love birds are there.
Since you asked, you may be interested in Thomas Smith's blog entry on the
Disney Parks Blog about the 200,000 lights which make Cinderella Castle look like "it's been dipped in sugar." Have a wonderful day and a magical honeymoon!