This does sound like a love/hate event . . . it sounds fantastic but the anxiety is oozing through even a short posting like yours. Why would you go on this cruise if you are feeling so anxious except for the opportunity? And why go with people who do not understand the role that your anxiety plays for you? And why a 14 day cruise? Could you not test out the waters (no pun intended) with a 3-day cruise before trying for a 14-day one?
But, let's assume you go . . . .this site as you know is full of management tips and tricks but this one I got from asking a neighbour who does have anxiety but who loves cruises (at least one if not two per year). She calls the cruise line and asks to talk to someone who is in charge of the medical services on board the specific cruise ship. She explains her situation and usually they ask her to fax them a list of her medications (prescribed, herbal, and over the counter) as well as any strategies that she might find useful for them to use. For example, on her first cruise alone, one of her triggers was what she now calls the Titanic event . . . even though the cruise was to the Bahamas, I guess she was concerned about hitting an iceberg (we still chuckle on this one). The cruise line made sure that one of the staff met with her at the beginning and explained safety procedures, etc. and they put some type of flag on her door so that should there be an emergency crew members would know that this person had special needs. She has traveled on several different cruise lines and all of them have been more than accommodating . . . because she does so many cruises, she is familiar with the procedures, etc. so she has little need to do that now. So, you may want to consider contacting the cruise line to let them know especially given that you are traveling with people who, for whatever reason, are not sensitive to your needs.
I know that some folks would recommend seeing your doctor for meds and that might be a possibility, but I am still left with the lingering issue of why you would put yourself in such a position when you feel so uncomfortable. If you do go, I sincerely hope that you enjoy the cruise and that you can overcome being with family members who seem unconcerned about your needs . . . in any event, take care of yourself. . . .KC