O.k., here's your model: the National Folk Festival, going on around the U.S. since 1934. It's a travelling, multi-ethnic festival, highlighting the cultures of each city or region it visits. The current approach is to spend three years in each location, to give local organizers the hang of it, with the goal of a festival continuing after the "National" organization moves on.
That link's to the generic background, on the web site of the National Council for Traditional Arts, here is the link to the info on the current festival.