Sounds like you're doing it right. And it must be tricky with a crowd that stretches right across the community - there are songs you'd be itching to sing that might not fit. (Like Solidarity For Ever)

There are songs that sound like they must be old hat and so forth that could come into their own on such an occasion, songs like Michael Row the Boat and If I had a Hammer. And We shall not be moved. People should know them.

Deep Blue Sea they might not, but it'd be easy to line it.

I'm not sure about never sing more than three verses, sometime people just want to keep on singing when they've got into it. I mean the kind of songs where one line or one word changes each time, for example.