The Family applies to all tunings and it is no obstacle what-so-ever to participate with an instrument tuned in any different way.
There is a recommended tuning used by a large majority of the circle members.
From bottom to top:
Bb F C G D A C D
Any kind of touch-style guitar instrument usually works. For maximum playing comfort (especially for beginners), we recommend the 8-string instruments made by Warr Guitars or Touch Guitars.