Rowling wrote the Harry Potter fantasy book franchise on which the blockbuster films and new theme-park attraction are based. Radcliffe plays the titular wizard in the movies.
The 20-acre, $200-million Wizarding World of Harry Potter attraction is to open to the public at Universal's Islands of Adventure Friday.
Rupert Grint, who plays Harry's friend and fellow wizard-in-training, Ron, as well as composer John Williams, who created the Harry Potter musical score, also attended Wednesday's private party at the theme park, The Orlando (Fla.) Sentinel reported.
Williams led the Orlando Philharmonic outside a replica of Hogwarts castle before a crowd that included
Orlando Mayor Buddy Dyer, Orange County Mayor Rich Crotty, Orlando Magic star Dwight Howard, members of the Wizarding World creative team, tourism industry leaders and other guests, the newspaper said.