RE: dress code. If hubby doesn't want to dress up, so be it. Formal nights do call for a suit or tux, but you have several options: you can eat in the buffet area that night, or you can go to your regular table in whatever clothes you are taking (remember, shorts are not allowed in the dining room for dinner, though). It could be your tablemates won't mind in the slightest! (This happened to us on a 3-night Carnival cruise a few years ago - we forgot his tie, in this case - and we ate at the buffet, which was fine. The next day our tablemates all asked "Where were you? We missed you!" When we explained what happened, several of them said they had been wearing polo shirts or something else equally casual.
Don't sweat the small things. Your husband may fine he will enjoy the cruise a lot better than he remembers - especially if you are both able to relax and just go with the flow.