Hello there Debra!
If you are planning on adding the Disney Dinning plan to your resort stay, I would go ahead and purchase it now. It will just make your reservation that much easier. But if you want to wait, you can just go ahead and make an advance Dinning Reservation on the 24th. There is a new cancellation policy that is going to be in effect when you arrive at Walt Disney World. Starting October 26th, the following restaurants will require a credit card number to guarantee your reservations and will charge $10 per person if your cancellation isn't made at least one day in advance.
1900 Park Fare, Akershus Royal Banquet Hall, Artist Point, California Grill, Cape May Cafe, Chef Mickey's, Cítricos, The Crystal Palace, Flying Fish Cafe, Garden Grill, Hollywood and Vine, Jiko – The Cooking Place, Le Cellier Steakhouse, Narcoossee's, 'Ohana, Tusker House Restaurant, Hollywood Brown Derby, Victoria and Albert's (cancellation policy is $25/per person), Yachtsman Steakhouse
Thanks so much for asking the Moms Panel! I hope this information helps you with your planning and if you have more questions, please ask away, we are always here to help! Have a Magical Time at the Walt Disney World Resort!