We will be cruising Feb 10-14. We will be packing what we would normally bring on a WDW vacation, shorts, t-shirts, polo shirts, blouses, and then for the evening affairs dockers for my dh and skirts and blouses for me and my two dd's. My dh will bring a sport coat for Tritons. Nothing too fancy for him.
You may want to add some sweaters for the nights out on deck. It can get a bit breezy and chilly out there.
I have seen some familys do the whole nine yards with tuxes and gowns but that isn't our family. We prefer ot be more comfortable than fancy. After all it is a vacation.
Hope this helps. Have a great cruise.