I wonder what kind of group singing you're dealing with. If you're singing with accomplished singers, that's one thing. My main concern is singing with people who don't sing very often. I hate to give my standard answer, since it has often caused me to be drawn, quartered, and left hanging in the breeze. I've said it before, and I'll say it again:
The best resource for group singing is the Rise Up Singing songbook from Sing Out! (if used judiciously)
The book has lyrics and chords for 1200 songs - but note that many of the songs are not suited for group singing. For example, people who try to sing James Taylor songs with a group, should suffer a fate worse than death.
In many cases, it can be best to avoid songbooks when singing with groups. You're better off with chorus songs and "old standards" that everyone knows.