Give each of them a day. Add a stop each to the trip in Waystop before you leave: the arcade, the trainer shop, the ramen place from the video. Their stop goes first that day and nobody edits it. A teenager who owns Tuesday will walk through your Wednesday.
Settle the food before you fly. One meal a day is theirs, one is yours. Night markets and food halls end the argument altogether because everyone orders from a different stall and sits at the same table. Convenience stores in Japan, Korea and Taiwan are the late dinner that nobody fights about.
Phones and data. An eSIM on each phone, installed at home and switched on when you land. Turn on shared location, pin the hotel in the group chat, and agree that a dead battery is the one thing that gets someone grounded. See the eSIM guide for how to choose one.
Start late, finish late. They will not be up at eight and the city can wait. Museums are quietest in their last two hours. Then the evening is the point: Taipei’s Shilin market opens around 4 p.m. and peaks between 8 p.m. and 11 p.m., Bangkok’s night markets run from late afternoon until around midnight, Hong Kong’s Temple Street comes alive after dark, and a Tokyo arcade at 10 p.m. is the memory they will keep.
The museum that works. Interactive and short. London’s Science Museum is free and its Wonderlab gallery, from £13.50 and aimed at 7 to 14, still lands with older teenagers who pretend otherwise. NEMO in Amsterdam sells timed-start tickets, so book the slot. teamLab Planets in Tokyo is a timed ticket too and sells out on weekends; book early. Ninety minutes, then leave while they still like it.
The independence radius. Agree it before the trip, not on the sidewalk. In Tokyo, Seoul, Singapore, Taipei, Hong Kong and Copenhagen a 15-year-old can take the metro three stops alone and meet you at a named exit. In Paris, Rome, Barcelona and Prague the risk is the pocket, not the person: daylight and a few streets. In Bangkok and Mexico City the group stays together after dark.
What they will remember. Not the cathedral. The convenience store at midnight, the time they ordered in Japanese and it worked, the wrong train, the stall where the cook laughed at the chilli face. Plan one thing a day and leave the rest empty.
The first morning. Say the one meeting time and the one meeting place at breakfast, charge every phone overnight, and let the owner of the day lead from the hotel door.