The only time shorts and thongs are allowed in the main dining room on the Sun Princess is at breakfast and lunch. For dinners during Smart Casual nights, a pair of slacks (not jeans) and a collared shirt (polo, button down cotton, island type shirt) are allowed. The Horizon buffet is casual all the time and shorts and thongs are allowed. Even in the Horizon you need to wear a shirt or a bathing suit cover-up. T-shirts are allowed. They also have a Pizzeria that serves lunch and dinner that are casual, again you need a cover-up and a shirt for men. They serve hot dogs, hamburgers, and sausage with french fries by the pool. Room service is also available. The dining room rules apply for both Anytime Dining and Traditional Dining. They turn part of the Horizon Buffet into the specialty restaurant during the dinner times.
Sure hope y'all enjoy the Sun as much as we did. We sailed on her twice when she was doing the Caribbean routes. Have a wonderful cruise!