We ate at both places on our trip that ended one week ago. I agree with the previous poster that the kids' selections at CP seemed to be there just to ensure that kids would find something that they liked, but they could eat from anywhere in the buffet, as could adults (they could eat the kids' mac n cheese if they wanted to).
As for Garden Grill, they bring out a platter of food for the adults, and a platter for the children. My dd had fried chicken fingers (big ones) and macaroni and cheese. She certainly could have eaten off of our platter, too, if she had wanted to and vice-versa. I think they will even bring you seconds on anything you want, though we didn't need it!
We really loved the character interaction at both places!
Have fun!