Always, always, always choose airline seats at the moment you book the tickets, and pay extra if you must. If you leave seat selection for later, there's a decent chance your family will be divided into three separate rows, what with flights increasingly being sold out or overbooked. And call the hotel with room requests, double-checking your preferences at check-in, or else you may have to listen to rowdy guests exit the hotel elevator well after kids' bedtimes.