i haven't heard that Crystal was going more casual, so on that note your best bet would be for days - shorts/top, bathing suit w/cover-up. Casual Evenings: nice pants and a collared shirt for your man - dockers type pants and a polo shirt are always a good choice, as for you- a nice casual sundress, capris and a nice top, skirt & blouse, or a nice pair of trousers with a blouse. If there is a semi-formal night(not sure) your man would need to kick it up to a blazer, dress trousers shirt & tie, and you would need to wear a dressier dress, dinner suit, dress pants/blouse that type of thing, as for formal nights - a dark suit/shirt-tie or tux for your man, and for you - a dressy cocktail dress, long dress, dressy flowy pants with a sparkly or silky top, dressy dinner suit.
We were on Serenity in 2005 after 2 RCL cruises. Crystal is definitely more formal and they require you to remain in the dress code of the day for the duration of the evening. As there is no buffet available for dinner, everyone must follow the dress code for the main dining room for dinner.