Welcome to planDisney, Gail!
Talk about the best surprise EVER! In the words of Bruno from Encanto, "You’re exactly what this family needs." I'm sure your mother-in-law will have the most magical time. Early December is actually one of the very favorite times to visit the Walt Disney World Resort. It's all decked out for the Christmas season and looks "practically perfect in every way." She'll be able to enjoy seasonal treats, festive music, and comfortable weather. I was literally just thinking, "The next time I book a trip to Walt Disney World, we need to go at the beginning of December."
Last year, I was able to visit The Most Magical Place on Earth in early December. Although the crowds are never low at Walt Disney World, the beginning of December is usually a good time to visit if you want slightly lower crowds. That's because kids are still in school and it's just after Thanksgiving. So there's a little window there before it gets super busy again. Midweek days are usually less crowded than weekends too. So I think you've picked a good time to take her, Gail.
I hope that's helpful! If you want to sprinkle even more pixie dust on her trip, you should consider getting her a ticket for
Mickey’s Very Merry Christmas Party. I attended this event last year and it was probably the best thing I've ever done at Walt Disney World. Minnie’s Wonderful Christmastime Fireworks Show is spectacular. Mickey’s Once Upon a Christmastime Parade is magical (there's even "snow" on Main Street, U.S.A.). And the crowds are a lot lower, which means it's really easy to get on attractions and move around Magic Kingdom Park.
I hope your mother-in-law has the best time of her life, Gail. Thanks for stopping by planDisney!
Mike