This is my personal experience from two previous cruises. Yes, you can rent a tuxedo from Disney, if you go on one of their 7-day cruises. The order form comes with your cruise documents. Frankly, I went all the way with what is called a "black and white." Black tuxedo jacket, white dinner jacket, two shirts, one or two pair of slacks, cummerbund, vest, one or two pair of socks, tie, studs (which I did not use), and cufflinks. Everything except the shoes, as I had a pair of black cowboy boots, which I wore. And all this for about $125.00.
The first time I cruised, I wore the white dinner jacket to the brunch at Palo's, and frankly, I was overdressed. The second time I cruised, I wore it to the 2nd formal dinner, and it worked out fine.
As for everything fitting, one of the first shirts did not fit, but, maybe that was because I tried to take the measurements myself. The second time, I had my
travel agent take the measurements, and everything seemed to fit fine. Indeed, my measurements are on file with my travel agent, in case I ever need them again.
Men have seemed to have gotten out of the habit of dressing for dinner in a tuxedo, even on a formal night, but, if you can get all the men in your family to do it, go for it. You'll have a memory you'll treasure forever. And be sure to have the family's picture taken before dinner. Many people do that, then use the family picture in their Christmas cards. Enjoy your next cruise.