Sunday Afternoons:  Slack Key Guitar Concerts.  Traditional Hawaiian slack key guitar and `ukulele concerts.  April 6 – Circle of Life; April 13 – Gift of the Ancestors; April 20 – Honoring Raymond Kane; April 27 – For the Birds.  Tickets: $20 ($15 keiki/seniors).  The concerts are nahenahe - soft and sweet.  Slack key guitar and `ukulele in the real old style.  All traditional music with songs and stories of the islands, telling the history of this Hawaiian musical art form.  A…