I travelled with my 17 year old son on the Majesty at Easter 2015.
We take a cruise holiday every year as a family and usually use American liners as they cater for teenagers. We have previously cruised on Thompson Spirit so we knew what to expect and that smaller cruise ships cannot compete directly with slides ,climbing walls, large pools etc.so we set realistic expectations.
The first night was relaxed listening to music in the bar and the next day I used the gym which was small but well equipped.
The room was adequate and kept very clean .