A couple of other factors to consider...
Kids 10 and over pay adult prices and order from the adult menu. Kids 3-9 must order off the kids menu if available.
Gratuities are not included at most restaurants. Assume a base gratuity of 18% (which is what Disney charges automatically for groups of 6 or more)... if you are regularly choosing the more expensive restaurants or menu items, the gratuity will be increased accordingly, so you need to factor that in.
Meals at CRT require 2 credits on the dining plan, so you will have to pay OOP for a meal sometime to make up for that.
Do you want to have table service meals every day of your trip?
Many people who purchase the dining plan say they do it for "peace of mind". But logically, I know that if my family eats the way we like to when on vacation we would never spend as much as we would pay for the dining plan (even the quick service plan). If you think you will enjoy your vacation more because you don't have to "worry" about what you're spending, go ahead and do it. But it's doubtful you're actually coming out ahead, financially.