Well I personally don't know how that situation would be handled on the ship, but I've traveled internationally enough with luggage that's over the weight minimum, and the worst that'll happen is paying extra. I'm sure they won't reject the suitcase for weighing more, maybe just charge you.
Also, the rules say that each guest can have two suitcases, weighing no more than 50 pounds each, so you may just be better off using two smaller suitcases. I might do that, as well as a carry on. A good trick is also sticking the suitcases on a bathroom scale, that way you'll know what you're in for.
Has anyone had issues before with bringing alcohol?