Online alarm clock for 12:41 am
As you hand the dawn departure to the next driver, set the 12:41 am alarm so they can take over the trip to the Tongariro track. Confirm who has the keys, route and meeting point before you step away. The alert leaves enough time to make that handover calmly before 1:00 am, without relying on a hurried message after everyone has settled.
Because the person taking over may rest before leaving, check the phone that will actually provide the alert. Keep the browser running, leave the phone awake and connect it to power if the battery is low. If the browser stops running or the phone sleeps first, the alarm may stay silent and the track departure can lose its planned cue. A separate phone alarm is a sensible backup when reaching the trailhead by dawn depends on waking promptly.
For a handover this late at night, leave the next driver water and a simple snack that can be eaten without delaying departure. Something familiar, such as fruit or a muesli bar, is easier to manage before the drive than a large meal. Save heavier food and another hot drink for a planned stop or for after arrival, and pack enough water for the early start.