I agree with Christy's idea of letting the students be in charge of coming up with ways to highlight their cultural differences. There does seem to be one problem with that as well. Students themselves are often hesitant to highlight their own cultures because of the fear of being "different" than their peers. They worry about not being accepted and to take the great leap of exposing a whole new culture, not sure of whether their peers will make fun of them or not, may be enough pressure where they do not care to share their cultures.
So if the "American" people in charge should not do it, and the students are too afraid... who is it that we turn to to help plan cultural events that will help others understand these different cultures? Parents would be a good place to start but it would also help to bring in people from the community, people that kids look up to, to help educate young people and adults in a way where the students do not feel threatened by it.
Kim