Hi Julie,
It really depends on what your family likes as to which meal is the best at Cinderella's Royal Table. If you would like to see characters whilst you dine then you should choose either breakfast or lunch where about 4 Princesses are present whereas only the Fairy Godmother tends to appear at dinner time which could disappoint younger guests. The only other differences between the 3 meals are the menus and of course the cost.
My family aren't big breakfast eaters so when we dined in the Castle we chose to eat at lunch time as, although slightly more expensive than breakfast, the menu suited us better. If you click this link
HERE you can view all the meals available at the Castle plus see links to the menus.
At the end of October Disney will be accepting dining reservations 180 days in advance again, this will mean that you can book your reservations on October 27th when the system changes. CRT is incredibly popular so I suggest you book on that day as soon as the lines open at 7am EST, you can do this by calling 407-939-3463 or online via the link above. Try and be flexible with your dining times for the best chance of securing a reservation.
I hope you manage to book a table and you have a fantastic trip,
Jo