Demi Lovato and the Jonas Brothers showed their support at Arthur Ashe Kids' Day in NYC this past Saturday, August 28th. Founded in 1969, this annual event is held to benefit the National Junior Tennis and Learning network. The recent birthday gal was all smiles as she performed solo and along side ex-boyfriend Joe Jonas—including a duet of "Wouldn't Change A Thing". Flip through to see the stars of Camp Rock 2 rocking the socks off of the crowd at the Billie Jean King National Tennis Center.