The most common form of a gay establishment is a gay bar and in areas without any this is the most common form of non-gay establishment to create a time and a place for gay men and lesbians to congregate outside of private parties or trips to isolated gay pride events.
This is in addition to their friends and supporters also known as the PFLAG community or straight allies in general.
With the case of theme parks it is often unofficial and simply organized by the visitors themselves or a committee that creates a group to approach a park or other amenity on a specified day.
Moreover, the theme parks tend to be apprehensive to being viewed as openly supportive because they attract a lot of families and conservative people that may be uncomfortable or unaccepting of homosexuals.
However, as attitudes have changed regarding the community this has changed to a tacit endorsement of the pink dollar with a more passive acceptance with such parks often stating they simply cannot prevent people from coming into the park based on arbitrary distinguishing demographics and that they do not endorse any privately organized group events at their parks.