A-list celebrities and even local celebrities can add to the excitement of your event. Celebrities make great emcees, but do not use them as your auctioneer. They are not trained and do not call auctions for a living. If you are going to have celebrities at your event try to market your event with their names in the advertisement if they are definitely booked. This will add a whole new draw to your event.
Try to stay away from celebrity attendees coming on stage and auctioning items; simply let them come on stage to promote an item and pump up the crowd and let the auctioneer do the bid calling. If you are going to have a celebrity as a guest speaker have the auction and fundraising first then the celebrity can speak after all the money is raised. Remember, you are there to raise money first and entertain second.