Both trips (November and April) we went to Casey's. With one counter service credit, we got hot dog, fries, drink and dessert.
I noticed a lot of people not asking for dessert, and the CM didn't go out of their way to explain to them that it was included on DDP. I ordered and was not charged anything extra. It was a lot of food, but the dessert (I think it was a Peanut Butter topped Brownie????) came in a small container that we stuck in the backpack for later.
If you are still uncertain, just ask the person taking your order. Something along the lines "and dessert is included with this, right?"
Have fun! Wish I were going back, but DH says two trips in one year is more than enough!