Dierks Bentley has announced that he and his wife, Cassidy, are expecting their first child. He revealed the news on his fan club site on Monday (May 19). The couple is currently vacationing in Mexico, where they were married on Dec. 17, 2005. Bentley wrote that they have been unsure about wanting to find out whether it's a boy or a girl but have decided to wait until the baby is born in the fall. Bentley released his Greatest Hits album earlier this month.