Thanks. We do a similar thing with Christmas carols, by the way. It's one area where a lot of people from different backgrounds have shared repertoire. People at my workplace used to have a group which led carol singalongs at every Christmas party (we called ourselves "Hell's Elves"). The group didn't survive a drastic office downsizing, but some of us still get together for a carol sing every Christmas.
The standard carols can get boring, but there are lots of really good lesser-known carols which are fun to sing, and you can find comprehensive carol books with lyrics to them.