I just looked at a couple of Cruise Compasses from our recent cruise on the Freedom. "Smart Casual" is listed for the specialty restaurants, which means trousers and button down shirt to me. But given the nature of fine dining one encounters, many guests dress up for their special night. On the formal nights for the ship, I would dress up for the specialty restaurants.
When we ate at the specialty restaurants, my husband wore trousers,shirt and sport coat. I did see on a few occasions others with sport coats and others without. Trousers & button down shirt would be fine. Enjoy! Lynn