Here is the info. from RCCL's web site. Hope this helps.
What is the dresscode for dinner?
There are three different types of "evenings" on board - casual,
smart casual and formal.
Suggested guidelines for these evenings are as follows:
Casual nights: We suggest sport shirts and slacks for men;
sundresses or pants for women.
Smart casual nights: We suggest dresses and pantsuits for
women; jackets and ties for men.
Formal nights: We suggest women wear cocktail dresses;
men should wear suits and ties or tuxedos (optional).
The dress code for children is no different. We ask parents to use
their judgement. Again, these are guidelines and your evening
attire is left up to your discretion. In addition, we do provide
alternative casual dining in the Windjammer Cafe onboard all of
our vessels on each of our formal evenings. (Please be advised that
the dress codes on some sailings may vary. Please check your
onboard Cruise Compass guide for information on your specific
sailing.) No shorts will be allowed in the main dining room