WDW is not the paragon of healthy eating establishments. Disney is also not responsible for the amount of food people place in their mouths while dining at the resort. If a server insists that your 11-year old order an adult portion (which I've never heard of, BTW), ask for an extra plate and place the portion you don't want him to eat on it. You could also order a salad as an appetizer or ask if you could purchase the kids' salad or veggie appetizer to go along with the mac and cheese.
Making 10 year olds Disney adults for tickets and dining is a money grab, plain and simple. It is what it is, but you can certainly do some research, read menus, and make healthy choices from the options given.
I'm sorry, I'm not very sympathetic. If you purchased the
DDP, you are very limited as to how you can order in the restaurants and you knew going in, even if paying OOP, what the age restrictions are. You also have access to all menus. Other than the caesar salad options (with dressing on the side!), there is nothing at 50's Prime Time which would fall under the "healthy" category.
If I were you, I would not purchase DDP, and would do a little more menu research before making your ADR's. We are a big fruit and veggie family and I do not purchase the DDP because we need flexibility in our ordering at WDW restaurants. We are always mixing and matching from the kids and adult menus for our DS so that he gets a balanced meal and he is limited to one treat per day while there. I actually think WDW has done a good job at introducing more healthy options in the kiosks around the parks. We can now find whole and cut fruit in the parks, whole almonds in AK, etc. Yes, lots of kiosks, in EP especially, with pastries and donuts bigger than my head, but, again, WDW is not forcing us to eat them.
Is Disney contributing to the obesity epidemic? Absolutely not. Make smart choices when ordering for you and your children and control the portions yourself!