At buffets & family style the 2 year old can eat whatever you want them to. At a la carte restaurants they need to eat off your plate or you would have to pay OOP for their food.
I've seen people report that at Ohana specifically, children's food (from Kona I think?) was brought out for under 3's without being charged for it, but we didn't personally experience that and I wouldn't bet on something like that happening consistently. At Garden Grill the kids option was brought out for us without us having to ask, but I think they may do that for parties with adults only too.
We found that with a 2.5 year old, buffets were wonderful, as we didn't have to worry about ordering something he may or may not have eaten and we could get him food as soon as we sat down. He also wasn't confined to the (IMO lacking) children's menus in order to get a child sized meal.