getting a handful of people - with no experience sailing - to charter a catamaran is going to be an eye opener for everyone on board. Your skipper can certainly handle the vessel but will need help in some things, and instilling good boat habits will be a daily part of the Captains routine - using the heads, conserving water, power usage limitations, organizational structure on many levels from personal cleanliness, galley duties, beverage intakes, shore excursions and safety aboard are all potential stumbling blocks that are not commonly evident on a shore based vacation.
Expectations on their part and pre trip meetings and planning on every-ones part are a worthwhile consideration.