In my experience (in England) it's hard to keep both singers and players happy. I'm seen a club where musicians stopped coming because they only got the chance to play a single tune when it was their turn in the circle; I've also seen one where singers were driven away by musicians who wanted to play together and had no patience with solo singers.

I go to music sessions, song clubs and mixed sessions, but I'm in a minority. Most people seem to have a clear preference for one or the other.Music sessions with a few songs can work well, but only if people stick mainly to chorus or shanty-type songs, or accompanied songs that everyone can play along to.

At festivals in England, there are normally song circles and music sessions at different venues or in different rooms of a bar, which seems to keep everyone happy. So your idea of separate nights for each might be the best solution - those that enjoy both can come to both, and you might get some useful overlap.

Mind you, I don't think I could get on with the song-sheet idea. It's not something we do much over here, and I think it would tend to remind people of school or church. Those who are too lazy or forgetful to learn songs do sometimes bring their own crib-sheets, though I think this is best discouraged. I've never heard a really worthwhile version of a song performed by someone reading all the words from a song-sheet. And choruses are more of a shared experience if everyone's not gazing at their own printed sheet. People can soon learn choruses well enough to join in, so there's plenty of chance for participation without a need for printed words.