You will have a great time!! As everyone has said, prepare to eat!! The food is usually very good. some thinf may not apeal to you if you are like me, a basic steak & 'tator man. But try it all, its FREE.
As fas as motion sickness goes, It all depends on the size of the ship. My first cruise was on a decent size ship, but you could feel it move some. I wore the wrist bands, and it helped. I didn't think they were working, so I didn't wear it one night to dinner. Bad move, I had to go back to the cabin to get it. Last year though we went on a Disney Cruise. Huge Ship. Never felt it move. In fact when we boarded, after getting settled in we went to one of the bars (big surprise). I turned and looked out and was amazed to see that we had been sailining for 30min or so. Never felt a thing.
Anddon't worry, there will be plenty of things to do, other than drinking and gambling.