While doing any outdoor activity with your Cub Scouts, each boy should have the following six essentials.
First Aid Kit
Cub Scouts will only need a small kit of their own. Their kids should have some adhesive bandages, moleskin to prevent blisters, antibiotic ointment (single use packages work great), and insect bite pain reliever. This is not a comprehensive list, but it will get your Cub Scout started.
Filled Water Bottle
Keeping your Cub Scout hydrated is crucial, especially when it is hot out. Everyone should have a water bottle that will hold enough water for the entire hike. If you're going on a longer hike and need to carry more water, a Camelbak hydration pack is a great solution.
For camping and to have at night.
Trail mix, granola bars, fruit... food that is healthy, energy boosting and does not need to be refrigerated.
We all know how important sunscreen is - even when its cloudy. Also a hat and lip balm.
There are two things your Cub Scouts need to know about the whistle: 1) It's only for emergencies, and 2) Three blasts of the whistle means "HELP!" It might be a good idea to practice the help signal before the hike or during a den meeting in order for the boys to understand the rules associated with the whistle.
Remember, everyone going on the hike, or camping needs to have their own (this includes parent partners and leaders). Each Cub Scout needs to carry these items in their own backpack.