Anne, it's absolutely all you want. Our DD is 10, and she ordered off the adult menu more than 1/2 the time. She had lobster on semi-formal night, and they gave her a normal portion (which she ate 3/4 of)! When you order steak and lobster, they only give you half the lobster, so I was pretty surprised that they gave her a whole one. Several times, she ate all of an appetizer and they brought another one.
This isn't just at dinner either. She really liked the smoked salmon that comes with the bagel at breakfast. I imagine she probably ate about 5 plates worth of it over a couple/three days! Once they figured out that I was eating the bagel, and she just ate the salmon, they just brought plates of it!
They are very accomodating about the kid's tastes. The only time it's a problem is if the item is already pre-made. For instance, she likes quesidillas (sp???) but said she didn't want the green onions. They are pre-made that way, so she tried them anyway, and decided that she liked them. They did put all the sauces on the side for her, so she could pick and choose.