JANN HENDRY/Acorn Newspapers TUNING UP BEFORE TAKING THE STAGE- Dick Van Dyke, second from left, rehearses with his quartet, the Vantastix, which includes, from left, Bryan Chadima, Eric Bradley and Mike Mendyke. They were rehearsing before a benefit performance at the Thousand Oaks Civic Arts Plaza last Sunday. Van Dyke also sang with five local high school choral groups.