I like the idea of a travel memory book or travel journal for kids. It's a great way to get the little ones excited about the trip, record memories and encourage a little creative writing or drawing practice. You can buy a ready made travel journal from a book store or if you like to be a bit crafty, there are some great printable and free options online to make your own kids travel booklet.
A travel scrapbook can showcase photographs from your trip as well as printed souvenirs gathered along the way, such as business cards, sweets labels, cafe napkins, and sightseeing entrance tickets.
Bring along some art supplies - markers, stickers, glue stick, ... Work on it during quiet time, during a long plane or car trip when they really don’t feel like sitting still! A forever keepsake to cherish...
For inspiration checkout:
Another way to do it : www.marthastewart.com/266957/vacation-memory-jars/