Plan a full family trip budget including all costs.
A family trip budget has three cost shapes and mixing them up is what makes estimates wrong. Accommodation is per night regardless of how many share the room, so it scales with duration only. Flights are per person and scale with party size only. Food is the one that scales with both, which is why it grows fastest: four people for seven days at 45 a head is 1,260 dollars, often exceeding the flights. Splitting the total into per-person and per-day figures shows which lever to pull — if the trip is too expensive, one fewer night saves the accommodation and food for that night, while a cheaper destination saves the flights.
Family Trip Budget
Accommodation = nights x nightly rate; flights = travellers x per-person fare; food = travellers x nights x daily food; total = all four plus activities and local transport
Food or accommodation, not flights. Food scales with both people and days, so on a week-long trip for four it commonly overtakes the airfare.
More than most people expect, because it removes both the accommodation and a full day of food for everyone — on these figures about 340 dollars.