From our 15 year-old volunteer:
We have already posted it on Facebook. Email probably won't be effective with our age group, everything is on Facebook now.
One idea to get word out to local kids and teenagers is to put signs in school gyms, and near the locker rooms. Fall tryouts for highschool teams start in just a couple weeks and kids will be in and out of the schools all day. Middle and Elementary schools will not be open until late August though.
I would also strongly recommend trying to get your flyers or cards into the local pools, country clubs, and grocery stores. They usually have message boards where signs can be posted. A lot of kids spend their whole day at the pool, so it would be a great way to get the word out to younger people.
And from a super star adult volunteer with a 10 year-old:
I was wondering about flyering at Youth Centers/ Pools, Cycling & Running blogs/clubs -- A few years ago one of our dogs ran from 14th street across Georgia Ave. and well into Takoma Park, almost to the MD side -- if it wasn't for the kids/teens out on playgrounds and skateboarding (and the promise of cold hard cash), we wouldn't have gotten our dog back... this reminded me of finding a way to target the kids. Children out w/parents have called out to me, "Hey we're looking for your dog" when they've seen me flyering ...