"Please Jim Enlighten me re incompetent singing.
You might start with being able to hold a tune and remember the words - not enough, but I'd happily settle for it for a start. When you've got that mastered, then perhaps you might go on to understanding and liking the song you are singing. I'm not asking for virtuoso performances; they will come later.
Speaking personally, I got very tired of feeling embarrass on behalf of would-be singers who made idiots of themselves in front of audiences; patronising a poor singer is doing nobody any favours - help them to be good ones and then give them an audience.
If you are serious about attracting new blood you owe it to the music to present singing at a reasonable standard. A new punter who walks in from the street and hears naff singing takes that impression away with them - that for them is folk music - are you happy with that image?
I totally agree with whoever said that you can't have interpretation from crib-sheets.
Cap'n' suggestion of running through your text in the jacks is an excellent one - and you make some wonderful friends in there.....! but not on stage - please.
If you are going to turn your club into a Freemasons lodge and only give access to the initiated - fine; you are entitled to perform your songs naked while standing in a bowl of custard; if you are a public club - you owe it to the music to set a standard - and to yourself. Nobody but a sado-masochist likes bad singing, from themselves or their fellow performers.
Singing can be fun - even if it's belting out Yellow Submarine five minutes before closing time - but for lasting pleasure and satsfaction you can't beat making a song work, knowing you've made a song work, and knowing that your audience knows you've made a song work.
Not unlike The Virgin Queen who said she had Calais carved on her heart; I have something MacColl once said in an interview back in 1980.

"Now you might say that working and training to develop your voice to sing Nine Maidens A-milking Did Go or Lord Randall is calculated to destroy your original joy in singing, at least that's the argument that's put to me from time to time, or has been put to me from time to time by singers who should know better.
The better you can do a thing the more you enjoy it. Anybody who's ever tried to sing and got up in front of an audience and made a bloody mess of it knows that you're not enjoying it when you're making a balls of it, but you are enjoying it when it's working, when all the things you want to happen are happening. And that can happen without training, sure it can, but it's hit or miss. If you're training it can happen more, that's the difference. It can't happen every time, not with anybody, although your training can stand you in good stead, it's something to fall back on, a technique, you know. It's something that will at least make sure that you're not absolutely diabolical
The objective, really for the singer is to create a situation where when he starts to sing he's no longer worried about technique, he's done all that, and he can give the whole of his or her attention to the song itself she can give her or he can give his whole attention to the sheer act of enjoying the song".
Jim Carroll