Planned around the ages you're really travelling with — budget worked out before you book, and enough downtime that day three doesn't fall apart.
One wants hiking, one wants the pool, the four-year-old needs a nap at one o'clock and the teenager wants the wifi password. Somebody always loses.
Not the flights you agonised over — the food, the entry fees, the ice creams, the parking. By day three you're well past the number you agreed.
Three things booked every day, everyone exhausted by Wednesday, and the bit everyone remembers is the argument outside the museum.
Passport validity rules, children's documents, entry requirements. All easy — and all impossible to fix the week before you fly.