Pack for the first six hours after arrival
Think through what happens between opening the door and going to bed: changing clothes, charging a phone, washing up, and getting ready for the next morning. Put those shared items in a bag that will arrive with the first group. Keep anything someone must personally control with that person.
Place the bag where it can actually be reached
A brightly marked bag buried beneath a week of luggage does not help much at a late arrival. Put it near the hatch or carry it with the passengers where appropriate. If you will leave larger bags in storage before check-in, remove the first-evening kit and any valuable or essential personal items first.
Check it at a vehicle handoff
Keep essential personal items with their user rather than relying on a shared suitcase that could arrive later. If the group changes vehicles, check the first-evening bag moved too. The goal is to find what you need without searching every case after a late arrival.
For example, if one adult switches from the train to a relative's car, ask where the charger and night clothes will be that evening. One person can say “the green bag is with me” before everyone goes their separate ways. At checkout, return the items to their owners so the first-night shortcut does not create a last-minute search.