Emerald princess hawaii

Just booked up to go on our first cruise for myself and my wife I'm 40 and she's 34.

Coming from the UK we've never done hawaii before, does anyone have any must do or definitely avoid? Also what's the age range of passengers like in January? With the longer stretches at sea would be great to socialise a bit.

Also I've not seen emerald princess mentioned on here so any reviews on what to expect would be great.