You can fill out the special needs form for a sharps container, but I'm my experience, it's been hit or miss being in the room when we arrive. I just ask the room steward for one, since that's what usually ends up happening anyway. As far as diet, being on a cruise surrounded by temptation makes it hard for any of us. As a newly diagnosed diabetic, your husband also still be figuring out how different foods affect his glucose levels. I do my best to keep it under control, watching carbs etc, but also don't beat myself up about over indulging a few meals on vacation either.
Went on two cruises last year and didn't gain a pound on either one. Did a lot of walking. Skipped the elevator and took the stairs quite often. Every little bit helps. Good luck to him.