New York City
Pick two neighbourhoods a day and stop trying to do the rest.
The most distinctive city in America, and the easiest to plan badly.
New Orleans is a food and music city that happens to have great architecture. Almost everyone's first trip is too Bourbon Street–heavy and too short. The version worth having is Frenchmen Street instead of Bourbon, the Garden District on foot, and at least two meals you plan the whole day around.
It's compact, hot, and best in the shoulder months. Three or four days is plenty, and a long weekend built around a festival is one of the best trips in the country.
Warm without the summer swamp, and the festival calendar — Mardi Gras, French Quarter Fest, Jazz Fest — lands in spring.
A workable shape rather than a schedule to obey — two fixed things a day, and room to change your mind.
Walk the Quarter, Marigny and Bywater. St Charles streetcar for Uptown, Uber for everything else. A car is only worth it for the swamp and plantation drives — parking in the Quarter is expensive and awkward.
The city runs on booked tables and shows, and the best restaurants take reservations weeks ahead. Split the bookings across the group rather than leaving it to one person, and keep them all on one shared plan so nobody double-books a night.