Set out the suitcase your kid(s) will use. This is a great visual, so they can see they can’t bring their entire stuffed animal collection. The tip here is DON’T let them actually pack the suitcase. They’re going to gather the items and you’ll pack them in the suitcase. This gives you the final view of what they’re bringing.
Prepare a packing list for your kids. The lists have varied during the years. Sometimes it’s all been handwritten on one sheet of paper. Other times it’s been individual slips of paper. I even tried a white board once. The idea is to get your kids to pick an outfit for each day of the vacation. Hopefully one of these styles will work for you or inspire you in your own list making.
Have your kids set out each “day outfit” and extras on the floor/bed. This is the time that helps you. While they’re working on getting their clothes gathered, you can work on your own suitcase.
Review and Pack their selections. Did they choose each outfit wisely based on the activity for the day? Did they remember underwear & socks? Now, using whatever packing method you like (I’m a roller!) you can pack their suitcase quickly.
Congratulate your kid and thank them for their work. This gives them ownership of the task (they won’t complain about any of the outfit choices because they picked them) and helps make them a part of the pre-trip preparation.