Mothers took the day off from work. Fathers fudged the ages of their kids (you had to be at least 10 to qualify). Boys in suits stood and boys in T-shirts slouched on the salmon rug, waiting for the audition that could take them to Hollywood. "YOUR CHANCE TO BE A MOVIE STAR!" was an offer hard to turn down.

More than 200 boys showed up at the J.W. Marriott Hotel downtown yesterday to try out for two lead roles in Lorimar's "Big Shots," a PG-rated comedy to be directed by Ivan ("Ghostbusters") Reitman. Those who did well will be videotaped today. Reitman will then select some of the children to fly to Los Angeles for additional screen tests between Aug. 1 and 10. Shooting begins in the fall.

In the film, scheduled for release in 1986, Opie, a white kid from the suburbs, joins Scam, a black kid from the ghetto, in "a search for their lost fathers," according to the information sheet given auditioners.

But how to choose from all these children?

"You have to picture this kid 50 feet high upon a screen and ask yourself if you want to pay six bucks to see them," said Lora Kennedy, one of two casting directors doing a 14-city search for the perfect six-buck boys.

Each boy hoped he was the one.

Anna Marra of Manassas said her son Chris, 13, has wanted to be an actor for years. "We were living out in the country, and he looked at me -- he was 5 at the time -- and he said, 'I want to be a star.' "

In preparation, Chris has been in three plays, has taken dancing lessons for seven years and has an agent. He's also been working with a speech therapist for three weeks to get rid of his lisp.

Next to Chris was Jonathan Singer, 14, who rode the subway in from Alexandria. It was his first audition. "I'm a lot less experienced than El Stud here," he said, looking a little worriedly at Chris Marra.

It was also the first tryout for Mark Felder, 7, of the District, but his grandmother America Nelson was there to help him overcome any shyness.

"Smile," Nelson said fiercely. He smiled.

Has he always wanted to be a movie star?

"No, he hasn't. Say, 'No, I have not,' " said Nelson.

"No, I have not," said Mark promptly.

Did he have to get up early to come to the audition?

"I don't know," said Mark.

"You got up at 7:30. Talk intelligently," Nelson told him.

"I got up at 7:30," he repeated. Mark played Santa Claus in a school Christmas play, which did not make him an aspiring actor.

"I'm shy. I laugh when I gotta go up on stage," he said, smiling angelically.

The Walsh family of Wilkesboro, N.C., may never recover from the audition of Chad Walsh, 11, who has been in three school plays but never tried out for a movie before.

Chad, demure in a gray suit with a red tie and matching red hankie, stood proudly in line, waiting his turn to audition. He weighs 145 pounds. "The reason I'm so big is they feed me turnip greens. They feed me so much turnip greens they have to tie a rag around my leg and put kerosene on it so the cutworms won't eat me up," said Chad, delivering his joke with a perfect deadpan expression.

"He's a real live wire," said his mom, Diane Walsh.

It was big news for Wilkesboro. Before he left for Washington, Chad did three radio interviews, two television interviews, and one newspaper interview. His schoolmates put up the sign "Good Luck Chad" on the school bulletin board, the mayor of Wilkesboro named him an official ambassador to Washington, and his uncle started calling him "Rambo."

"I know it's the biggest day in his life so far," said dad Kenneth Walsh, adding that Chad planned to deliver a get-well card to the president. "Maybe President Reagan can give him some pointers on his acting."