Miles and Music for Kids has been going for seven years now, and no wonder — it’s the perfect approach to the benefit show concept for a contemporary country star like Dierks Bentley. His event starts with some engine revving — not Chevy trucks in this instance, but Harleys — on a one-hour ride to downtown Nashville. Then there’s the cumulative star power. Besides Bentley — whose latest album has yielded one particularly artful patriotic ballad and two party-hearty chart-toppers — the lineup includes Sheryl Crow (who always seems to be up for a country collaboration), a newly solo Kix Brooks, amiable neo-trad crooners Chris Young and Craig Campbell, and Southern hard rockers The Cadillac Black and Brantley Gilbert, the latter of whom has a bad-boy-biker-with-a-heart-of-gold image at the ready. And it’s a good cause that anyone anywhere on the political spectrum can get behind: Vanderbilt Children’s Hospital.