A bit fancier, but knowing Cub Scouts you'll need something that is easily re-connectable.

I might suggest using the spring-loaded toggles that might be used to tighten cord around a sleepiing bag or a hood. Insert both ends of the cord through the same side of the toggle. The force of the toggle's spring keeps it fasten, but if pulled a bit hard, the cord will come out of the toggle.

I bought "ball cord lock" toggles (50 cents each) from http://www.therainshed.com - nice people. The round lock feels better on a bare neck.

I might suggest you use a narrower cord than paracord to make it easier to insert in the toggle lock. I found some orange "Sportsman's Cord" while a Walmart a while back. It was in the outdoors section and come on a small spool about 3 inches across. Works well as a lanyard cord for light loads (compass + whistle).

By the way, another idea is to get whistles from http://www.orientaltrading.com . Item # IN-20/45 . They are only $2.95 for 12 of them!! And they come on a wrist bracelet that is pretty comfortable. They are surprizingly loud too. They come in assorted colors. Make sure you buy enough to not give pink ones to boys.

I had my Cub Scouts put together a small survival kit:

Whistles from http://www.orientaltrading.com
Fanny Packs from the same place - Item # IN-16/257
Orange 33 gallon plastic bags - check w/ your local highway dept. I bought them from http://www.spectrumbagsonline.com/
Microlights - I found some big discout Princeton-Tec microlights on Campmor.com - looked like they were leftovers with a logo printed on