Princess - at least in the past - used to sell packages of wine (3 or 6 bottles) on a (presumably) per cabin basis. Might be better going for that. Or if it is still offered, bring your own onboard as it may be cheaper even after the corkage fee (may not be applicable as I understand the corkage fee has been increase significantly).

I couldn't find any terms explicitly specifying everyone had to buy the same package (barring age) but couldn't find anything explicitly stating that everyone didn't have to, either.