Hundreds of different languages are spoken around the world, meaning that "Hello" or similar greetings have hundreds of translations and manifestations. However, words are not the only difference in greetings around the world. The gestures or body language that people use vary greatly from culture to culture. Have the group learn how to greet people in a series of different languages with the correct body language. Examples include: "Hola" and a kiss on each cheek in Spain, "Namaste" and a slight head bow while pressing the palms together at the chest in India and "Konnichiwa" and a full bow from the waist in Japan.
Many people around the world wear clothing instead of or in addition to Western-style pants, shirts and shoes. Have the group learn about the wide variety of fashion articles worn by peoples around the world and immigrant groups, too, due to cultural or religious reasons. Three examples include teaching the group how to wrap an Indian woman's sari, a Sikh person's turban and a Muslim woman's hijab head covering. If possible, have supplies for each person and allow him to try to accurately create the fashions as explained by the teacher or facilitator.
Urban cities around the world have lots of restaurants featuring international cuisines. Even so, your group may be unfamiliar with many cuisines of other countries or the more traditional foods of cuisines with which they may already be familiar. Lead the group in a cooking workshop to create a number of dishes from different cuisines, or else a typical full meal, including appetizer, non-alcoholic drink and dessert, from one type of cuisine.
Movies from other countries, that are subtitled or dubbed into English of course, are a great way to introduce your group to other cultures. You can start with a film in a genre they may have heard about, like a kung fu fighting flick from China or a Bollywood film from India, or else you could opt for something completely different that they have probably never heard of. Lead a discussion of the movie afterwards using some questions you have prepared in advance as a guideline.