If you have the budget for it, I’ve always felt an actual celebrity appearance at the event is the best way to go. It really makes the people coming out to support your mission feel special and like you appreciate them. You have lots of options for appearances. At the most expensive end of the spectrum is putting on a performance, but you could also contact a celebrity for a speech, a panel discussion, or to do live autograph signings. Getting your celebrity endorser to talk about why they support your cause can help provide the initiative for others to contribute.
Another good way to bring in donations is to offer celebrity photo ops to your event attendees. With both live autograph signings and photo ops, you can arrange for part of the fee for an autograph or photo to go to your charity. Don’t try to do everything at one event, but choose one or two options that fit best with your goals.