Hi
As a former Eagle Scout, I did LOTS of hiking up in the Sierra Nevadas, and a fair amount in the deserts around SoCal with my troop. At the very least, the scouting leaders made us have a whistle around our neck and a pocket knife (usually in the BSA nylon holster on our belt). But you're right in that they usually don't carry much while running around.

What I found, around the time I hit First Class (what, about 13?) is that the Army-Navy stores have TONS of bags and such. I had a small old cotton pack that carried my 10 essentials (minus the canteen) that I kept on my belt. If you can get each Scout to carry something about 5x7 inches (maybe a tad smaller) that their 10 essentials can squeeze into, they're probably more likely to take it. An added bonus, "army" stuff might be better accepted than "fanny" packs or daypacks (the 'cool' factor).

Of course... YOU are the ADULT. That means, if you have to, the rules become "no exploring without the 10 essentials."