They're billed as your average teen-age computer whizzes, but the 20 youngsters Atari Inc. has picked for a new "youth advisory board" include a few celebrity ringers--such as child television star Todd Bridges and the sons of Washington banker Joseph L. Allbritton, television personality Nancy Dickerson and the owner of the San Francisco Giants.

Atari says it will use the children for "valuable input" on new computer and software designs and as spokesmen at trade shows. Several of the kids are being flown to next week's Consumer Electronics Show in Chicago, and the company had them all out to its California headquarters recently for a three-day "brainstorming" session.

As compensation, the company says, the youngsters are receiving a new Atari 1200XL computer system and expenses for trips on company business.

The computer company says the kids were selected after a nationwide search by a New York consulting and public relations firm headed by former White House social secretary Letitia Baldrige. But they concede that the names of Robert Allbritton, John Dickerson and David Lurie--whose dad is Giants owner Robert Lurie--came from Atari's president.

An Atari spokesman said that while the fact that the children had noted parents "certainly wasn't a prerequisite. . . . It certainly didn't hurt, though."

But young Allbritton, Dickerson and Lurie are no slouches when it comes to computers. According to Atari promotional literature, the 14-year-old Allbritton, son of the chairman of Riggs National Bank, is "capable of programming in several computer languages" and runs a computer network from his home in the District; 14-year-old Dickerson, of McLean, has written computer programs for an insurance company and is "conversant in three computer languages," and 12-year-old Lurie "is no computer novice" and writes programs in two computer languages.

And actor Bridges, the 17-year-old co-star of "Diff'rent Strokes," "has become an avid computer fan during the last couple of years," according to Atari. However, the company emphasizes, "acting remains Todd's main focus."

The other members of the advisory board aren't exactly refugees from video arcades. Fifteen-year-old Tracy Cullinan, of Los Altos, Calif., has started his own software company, Atari says, while Musa Mustafa, 15, of Walnut, Calif., is working on a computer-animated film for the 1984 Olympics. Board member Maria Michelle Smith, 16, also of Walnut Creek, got interested in computers at an Atari computer camp last summer. "When I got home, I cried because I didn't have a computer," Atari quotes her as saying.

Atari says it has outfitted the 20 youngsters' 1200XL computers with telecommunications equipment that will allow the advisory board members to communicate with each other through their computers. A spokesman said the company will regularly consult with the teen-agers and will fly them to California every few months for meetings with company officials.