Ashley and Mary-Kate Olsen
08/25/2004 at 02:00 PM EDT
Mary-Kate and Ashley Olsen haven't even started school in New York yet, but they're already planning a trip – to Miami, where they'll be presenters at Sunday's MTV Video Music Awards, a source tells PEOPLE.
The show will mark their first public appearance since Mary-Kate's six-week stint in treatment for an eating disorder earlier this summer. Sunday's show will offer the 18-year-old stars a chance to personally thank fans for their support, according to the source. A spokesperson for the Olsens declined to comment.
The pair recently moved from Los Angeles to New York, where they're preparing to begin their freshman year at New York University.
Sunday's VMAs also will include appearances by Jennifer Lopez, Gwyneth Paltrow, Hilary Duff, Lenny Kravitz and Jon Stewart, among others, as well as performances by Usher, OutKast, Christina Aguilera, Hoobastank and Jessica Simpson. Top nominees include Jay-Z, who's up for six awards for his gritty black-and-white video "99 Problems," and his girlfriend, Beyonce, who's up for five trophies alongside No Doubt, OutKast and Usher.