Hi Judy!
Congratulations on your upcoming anniversary! Disney World is the perfect place to celebrate such a special occasion.
For the most romantic meal at Cinderella's Royal Table I would choose dinner. Lunch is a character meal, and can be more hectic and noisy than dinner in the castle. At dinner, the Fairy Godmother comes out and does a little presentation announcing everyone celebrating a special occasion - like your anniversary. The menu is prix fixe, and you get a choice of an appetizer, entree, dessert and non alcoholic beverage. The current price is about $58 dollars per adult and includes tax, gratuity, and a photo package of you with Cinderella taken before you're seated. The atmosphere in the castle is wonderful and the photo would be a great memento of your celebration.
Another option for a romantic anniversary dinner would be to dine at the
California Grill at the Contemporary resort. Make a reservation during the Wishes fireworks at the Magic Kingdom, and you can watch while you enjoy your meal.
Whichever you choose, be sure to call and make your reservations 180 days in advance.
I hope this helps! Have a magical celebration!