I personally do not recommend it. I am a military sexual trauma survivor and whenever I see someone in uniform--especially an officer I find it very triggering and my depression as a result can last for day.
I know that the uniform is a trigger for most with MST and with 26,000+ rapes in the military each year there is more likely than not a MST survivor--or a friend or family of a survivor on that cruise ship.
I'm sure your friend is a wonderful person and this and that. But to support the thousands of honorable veterans who are suffering from their time in service I think it's best to not wear your uniform. Everyone deserves to have a good time and not be triggered.