Sentence:  Visitors to the Wests′ weekend <WSD>open houses</WSD> would often include Gore Vidal, David Niven, Vatican power brokers, ex-Queen Frederica of Greece and members of various superrich families, including the Vanderbilts, Guggenheims and von Furstenbergs. 
Meaning of the word marked with <WSD> tags:  An event, often in one's home, at which there are few restrictions regarding who and how many may attend.