I'm not on Atkins. The only similar diet I've done is Dukan. I do not have inside knowledge for you.
But what I can tell you is you're awesome, and you're going to be fine. Follow your plan and if you can avoid changing it because of the cruise, then avoid it. But if you won't enjoy your cruise because of it, then alter it for the cruise. You can always go back to square one to get back on track, and depending how long your cruise is I bet you won't be too far off track.
Best wishes! And keep up the awesome work!