Hi Trina. December is a delightful time of year to visit Walt Disney World Resort! Get ready to experience breathtaking decorations with plenty of "spirit of the season" inspiration sprinkled in to your already sure-to-be magical vacation!
You are
absolutely correct that Magic Your Way tickets can be upgraded during your trip, prior to expiring. Simply visit a friendly cast member at the gate in person with some remaining entitlements still on your ticket and within 14 days of first use.
It really does make a lot of sense to take the "wait and see" approach before adding
any special features like the
Park Hopper or the
Water Park Fun and More Option. It's very easy to develop a park touring itinerary from home only to discover upon arrival that a family has become ill, the weather is not what you would find most enjoyable for swimming or members of your travel party prefer a more leisurely pace and are no longer interested in visiting more than one theme park each day.
Wishing you plenty of pixie-dust this December! Please feel free to send more questions my way!