Rohanna, I can well understand what you speak of regarding family traditions - my many years of family reunions have had similar practices. And, not being familiar with what may constitute a "Pow Wow" outside your family gatherings, my only comment would be that any precedence beyond first come first served may be the agreed upon norm for a communal gathering. In the case of a purely public gathering, the organizers may apply rules which do or do not meet the *desires* of all who may wish to attend.
You point out that your desire/expectation of any different practice than that established for an event governed by family culture would be rude, and while you don't say so expressly, I presume you mean the same would apply regarding a request for a practice other than is in place for a public event. But I did want to ask if that is so. My posts are not always as clear to others as they seem to me, and your statement that "cultural or personal preferences apply" had me wondering if you meant either applies, or one applies unless the other contradicts, or simply that majority view should apply. Because postings can be open to various reads, I do not mean that as a snarky question, but literal reader that I may be, wanted to ask for clarification.