Hello there Gisella!
I don't think it's too late in the planning process! I would definitely try to get your dining reservations made as quickly as possible though. Fortunately, The dates that you are going are generally less crowded times for Walt Disney World so you may not run into too much of a problem making reservations.
In my opinion, there are two types of planners. Those who make their dining reservations, after looking at their planned schedule of which park they are going to be during their stay. And the other group, who starts with the dining reservations and plan their days around the meals. The latter makes planning the easiest when it's all about the food and reservations are hard to come by. I myself, enjoy the rides and being at the parks until they close so I am part of the first group who plans the meals after I choose which parks I will be going to on a given day.
Whichever method you decide, is up to you. Before you make the call, I would go ahead and figure out a general list of restaurants that you would like to go to. There are so many different ones that it gets overwhelming. Having a list handy really helps out when you are on the phone with guest services.
I myself like to go to at least one Character Breakfast, two nice diners, and one diner show during my weekly trips. If you can plan that, it's a great start. If you are on the Disney Dining Plan, then you will need to make additional reservations for other days. The cast members will work with you to help you make your reservations and it should be really easy for you... To make dining reservations, book online or call (407) WDW-DINE or (407) 939-3463 up to 180 days prior to your visit. I hope you and your family have a Magical Stay at the Walt Disney World Resort! Thanks for asking the Moms Panel! If you have more questions, we are always here to help!