First of all about the 'included' food, it's true that they advertise with all-inclusive. But it means that you get breakfast, lunch, some snacks, and dinner for the price. Most drinks are excluded, coffee for breakfast is quite regular so you'll get that. About the ice-cream I don't no the details but I think it's excluded.
Dinner is formal, you can choose wich seating you prefer. There are a couple of restaurants aboard, you'll get a table in one. And there are restaurants wich offer you special food for and additional fee.