Willie Nelson is looking happy and healthy, and just might be the youngest 87-year-old in the music business, based on his appearance Wednesday for Jimmy Kimmel Live.Flanked by his two sons Micah and Lukas, all on acoustic guitars, the country legend performed “I Never Cared for You,” a song he cut back in 1964.The Nelsons are one musical family.The patriarch has had well-publicized health struggles in recent years, but his appearance on late night TV suggests he's not short of energy (or