Hello Seana!
Welcome to the Disney Parks Moms Panel! I have a few suggestions for you...
Yes, it is possible for Cinderella's Royal Table to open up just prior to your departure. I've seen it happen on rare occasions as guests change their itineraries last minute, but it's best to have a back up plan.
What intrigues you most about this Dining Experience? If it's dining in the castle, try booking
Be Our Guest Restaurant, located in Beast's Castle in the New Fantasyland. I had the opportunity to dine here in December. Walking into the Main Ballroom and experiencing its majestic beauty brought me to tears; it will not disappoint.
If dining with Cinderella herself was your main caveat, try booking
Cinderella's Happily Ever After Dinner, located at Disney's Grand Floridian Resort. Although characters are subject to change, you'll typically meet Cinderella, Prince Charming, Drizella, Anastasia and Lady Tremaine.
Another hidden gem of both castle and Disney Princess experiences would be
Akershus Royal Banquet Hall. The delicious all-you-care-to-eat family style selections and complimentary image packaging make this a close runner up to Cinderella's Royal Table.
Visit us again with your questions, Seana, and have a MAGICAL trip!
Sherri