I volunteered last week at Brown Bagging 4 Calgary Kids - they make lunches for school kids who don't have a lunch or enough lunch. They and their community partners currently make 3800 lunches every school day. I don't think they can handle 20 in their location, but perhaps give them a call and see.
https://bb4ck.org/
At my old work, we used to volunteer at the Calgary Reads Book sale, helping set out/sort books. That's a very limited time period, just around a week in May, but it was lots of fun.