RIVERSIDE, Calif. -

The completion of a 2,500-mile scavenger hunt-type race that began a week ago will be celebrated tomorrow with a downtown Riverside extravaganza. ``Fireball Run 2013 Adventurally'' began Sept. 20 in Longmont, Colo., and concludes with a parade along University Avenue in Riverside, beginning about 2 p.m. Saturday.   After the parade, there will be an outdoor music concert, an ``exotic'' car show, barbecue, public safety displays, a beer and wine tasting, kids' recreation and a movie -- all on the Main Street pedestrian mall, between Mission Inn and University avenues.   The event is slated to wrap up around 9 p.m.  The annual Fireball Run Adventurally races bring together celebrities, business moguls and everyday Americans to take part in a trivia game that requires teams to solve clues to win -- all the while driving from one region of the country to another.  This year's four-state race, which doubles as an awareness campaign with the goal of locating missing children, has featured 40 teams canvassing as much territory as possible.  ``Not only will the Fireball Run event be a fun attraction, but it serves us all in a more important way,'' Mayor Rusty Bailey said. ``The Fireball Run's main purpose is to reunite lost children with their families, and Riverside is proud to be an integral part of such a great cause.''  During the race, competitors distribute posters with information about children who have gone missing in the areas through which they're traveling, according to organizers. Thirty-eight missing minors have been recovered since 2007, thanks in part to the Fireball Run Adventurally races, organizers said.   Participants in this year's event include former astronaut Jon McBride, Lamborghini chief test driver Valentino Balboni, professional rodeo champion Shea Holbrook and ``Car Warriors'' host Ray McClelland.   Portions of the eight-day contest are being livestreamed at http://www.fireballrun.com/live/stream