Hmmm; that depends... If a park advertises, it should mention that they are only open to certain groups, closed on certain 'special' days, etc.
Suppose I see a commercial or read an advertisement, telling me about a wonderful theme park that's open every day from 09:00 till 22:00 hours, except on sunday, and nowhere in the commercial or ad do they say ANYTHING about being open only to certain groups... And suppose I travel there, only to find out that It is closed to me... Then, in my opinion, I would have every reason to be upset.