If you are using guitars in Church why not use music written by a guitarist? Graham Kendrick has some wonderful songs, usually based on bible verses Servant King being my favourite. Taize songs are great too, but never the same in a church as they are in Taize itslf. Anyone can go,any age, its great to sing in a variety of languages with the wider Family..
Sacred Harp, or South Yorkshire carol style is good too, but rather rowdy for a reflective service I think.
We sand Turn, Turn Turn at a Hungarian wedding so it does show that anything goes...