i think that your pantsuit will be just fine, especially on a casual night. The no-jeans policy is for those who would consider attending a fine restaurant looking like they just left the job-site and were running into McDonalds ( for lack of a better analogy) . What the cruise lines really don't want (imo) are torn, worn, rattly, faded jeans with t-shirts in the main dining room. I really don't see anything wrong with a nice pair of clean, crisp jeans and a nice jersey polo type top with sandals or casual shoes for casual night.