One tux should be fine. Don't bother with the extra bother of a white jacket. I never saw any.
I sailed on the QE2 in May and took two formal pantsuits, mostly because I hate dresses. I found that two were plenty and wore each twice. A skirt or silky pair of black pants and a couple of sparkly tops would be fine also. I found that the dressy, silky-type pants packed well and took up little space. A pair of silver and gold open-heeled shoes worked with both outfits.
I had been worried about the bother of all this formal wear but ended up loving it and am planning on taking another cruise solo next spring.