Where I live, we have a soup kitchen where kids can help (they do have to be 13).
There is a yearly toy drive and wrapping drive during the holiday season, and kids get together in groups to help sort and wrap and tag gifts for other kids.
Our food bank takes a lot of what we grow here, which is a nice reminder for my kids about helping others.
My Dh is the Deputy Chief of our FD and I was a FF/EMT with the same dept until this January...our kids wash rigs, help with things like yearly fundraisers, etc. They are allowed to actively volunteer as Cadets at 16.
Our 4-H group is service-oriented, and the kids (14.5, almost 12, and 6 now) were very actively involved in helping set up a library, including collecting, stamping, and posting TONS of books to a small town up here (Alaska). They also have had spaghetti feeds and dances where the kids do the cooking, cleaning, serving, etc., to raise funds for different things (like kids with cancer).
edited to add: You might look into your local Red Cross. As many issues financially as they have, if there is a fire and a family loses its home, you can ask to be notified so that you and your children can collect and donate age-appropriate and household items. Teenagers especially seem to get left out when a home burns, and they end up with very little while the family gets new cookware and the little ones get new clothes and toys.
love, penelope