Chicago collective Kids These Days was a last-minute addition to the Bele Chere lineup (after Mambo Sauce dropped out). But the group of classically and jazz-trained musicians, ages 17-21, are well-worth catching. They blend elements of jazz, singer/songwriter and hip-hop into a fresh and upbeat sound. They perform on Saturday, July 30 on the Battery Park Stage, 6-7:30 p.m.