I'm afraid one came after the other. I stopped as a parent helper when the Cub moved up to Scouts. My youngest had arrived and It was getting a bit tricky doing the outdoor activities with a baby in a back carrier.
It's an award that can move up to Scouts, like the staged awards (hikes, nights away etc..), so it's possible to mention to your son's Scout Leader if they don't know about it, possibly put them in touch with the people who do the tidy up. We have a local environmental goup who monitor local becks and streams that feed into the local rivers for lifeform diversity, rubbish, nitrate pollution etc, and they're alwats grateful for the help that Cubs and Scouts can offer in the way of hands on the job. Cubs love nothing more than pulling old traffic cones and car tyres out of streams!