My first cruise I tried to do so many of the suggestions that were on threads, and in the end ended up bringing a lot of stuff home that we didn't even take out of the suit case. I took snacks for the movie theater, extra duck tape, a small sewing kit, loads of extras that just weren't needed.
Find in the Trip Reports section a 4 day and see if you can find a navigator( the daily schedule while on the ship) and see what things might interest your group. Watch
Youtube trip reports.
They do take a picture of your group when you board, my daughter and I went on a 3 day a few years ago, so she made us matching tank tops and we wore the same color shorts to have our picture made in. It was fun to do that.
Have fun, relax and enjoy the cruise.