When I am scheduled to have lunch with candidates, I never brought up any topics related to work, unless the candidates did it by themselves. It is exhausting to have an interview of 4~5 hours, and talked about your projects or work experiences many times. So at lunch, it is best to relax and eat. The candidates have to be well prepared for the afternoon. It is never to our best interest to make the candidates so exhausted so that they might not be able to perform well and thus we might miss good potential employees. So I prefer to have light conversations, no work . If the candidates fly from other cities, I will introduce the city, the neighborhood, and the life around. If the candidates are interested in any specific parts, like housing, schools, parks, bars, restaurants, etc. those would be very good topics.