We took my 18-month old nephew with us in September, and the pp is correct that children under three are allowed to eat at buffets with no charge. All of the ones we did also brought him a beverage in his own cup (usually milk) and we were never charged for it.
At two of the three non-buffet TS we did on that trip, he was also brought his own beverage, and at one he got a little plate of mashed potatoes and the other brought him rice (one of his favorite things). We all gave him little pieces of our steak/chicken/fish/vegetables, and he never wanted for food.
The third non-buffet TS (Coral Reef) did bring him a drink, and we bought a side of mac and cheese. I think they charged us $4 for it, and that was completely fine - we considered the treatment at the other places 'extra magic' and were always prepared to buy his little dishes wherever we went.
We always had fruit or other snacks for him in the diaper bag too, and he and his 4-yr-old brother (who did have credits) were just fine splitting CS meals. We always had extra fries and stuff too off of the adults' plates, so we never did purchase anything for the little one at CS restaurants.
