Yes, please give double Cruise Points to solo travellers. Your biggest competitor, Royal Caribbean, does that. Also, Carnival's sister cruise-line, Holland America, gives bonus Cruise Points for onboard spending as well as for passengers paying for Suites. All spending with the cruise-line should be respected as part of onboard totals, just as Holland America does: e.g. spa treatment, gym services, health products, speciality dining, shore excursions, drinks, et cetera.