The Wanderlist Kit of course. It is small (12 OZ) and fits into any pack. You can add items to it to make it more you. I added a knife to mine for added safety. In the winter I like to keep "Hot Hands" to warm up on a cold day.

Best advice: Snacks Snacks Snacks. LOL. Whenever I am hiking with my kids they ALWAYS need to stop for a snack. The best snacks that give them energy and are easy to just keep in the Wanderlust Kit are Chomp meat sticks, granola bar, and fruit snack gummies. Those are my go-to hiking/outdoor snacks for kids. We also play a game where they get to bring one lego or other small toy and find a place along the trail for the lego/toy to get their picture taken.