DCL does rent tuxedos but since DH has only ever worn a fancy suit for our wedding (42 years ago), it is highly unlikely that he would ever want to spend the money for a tux--rental or purchase.
Some people prefer to go to Beach Blanket Buffet (which is a sit down dinner) for formal and semi-formal nights. But, we like the "show" of the restaurants so we have never done that.
We go to the restaurants and I want you to know that even on Formal night we have seen men in shorts and women in sun dresses. The range of clothing runs the spectrum.
Since we are flying on Delta and have to pay for our luggage it is highly likely that DH will bring a sports jacket, dark slacks, a white shirt and one tie for formal night and a blue shirt and different tie for semi-formal night.
Do what works for you both. It is your husband's vacation too.
Jan/Kana