I am so sorry for your loss. It's definitely very cool that you are looking into volunteering at this point. I have a few suggestions for you.
Activate Good - They are hooked in with a ton of local non-profit organizations, and you can search for what you may be looking for by category. This may be the best "umbrella" resource around.
Others that I've had a good experience with....
Note in the Pocket - They provide clothing to impoverished and homeless children in Wake County. The woman who runs this is phenomenal and does so much for local children.
Food Bank of Central and Eastern NC - You can help sort and box foods, and it'd be a great activity for a teenager.
Stop Hunger Now - Prepare meals for impoverished families. They provide a fun environment, and share a lot of good info about the problem of Hunger in the world and what you are doing to help.
Brown Bag Ministry - Prepare brown bag lunches for local families in need. You can go deliver to the families if you choose. They deliver to many of the same people each week, so they are friendly encounters. I took my 8-year-old son to both activities last month. This group is doing great things, and it made a very positive impact on my son.
Best of luck!