With a multitude of balloons -- red, white and blue -- hastening skyward across the West Front of the Capitol and a flag-waving audience assembled on the Capitol's West Lawn singing "God Bless America," Washington's official celebration of the bicentennial of the Constitution was over.

"For almost 200 years we have lived with freedom under the law, and perhaps we've become complacent about it," President Reagan had told the crowd assembled in front of the podium. "We should never forget how rare and precious freedom is. Active and informed citizens are vital to the effective functioning of our constitutional system.

"All of us have an obligation to study the Constitution and participate actively in the system of self-government it establishes."

Facing the Mall, the West Front of the Capitol was festooned with large flags -- bicentennial and United States -- and a banner emblazoned with the Constitution's first three words, "We The People."

Across the lawn and wrapping loosely around the Capitol Reflecting Pool, a crowd estimated by the U.S. Capitol Police to be between 100,000 and 120,000 stood dense and colorful.

"This wasn't meant to be a birthday party, but a reaffirmation," ABC Television news anchor Ted Koppel, the master of ceremonies, told the audience yesterday. "It is an invitation to get involved."

Part civics lesson, part pep rally and part patriotic talent show, the program began shortly after 11:30 a.m. with the National Children's Choir singing "The Star Spangled Banner." Next came brief speeches by Senate Majority Leader Robert C. Byrd (D-W.Va.), House Speaker Jim Wright (D-Tex.) and Chief Justice William Rehnquist, and ended almost three hours later with President Reagan leading the audience in a recitation of the Pledge of Allegiance.

Before the official part of the ceremony began at 1:30 p.m., schoolchildren whiled away the hours, providing an informal alternative to the on-stage entertainment of bands and choral groups. In one fenced area, children from St. Peter's School in Waldorf, Md., vigorously waved flags, held constitutional memorabilia in the air, displayed computer printouts that read "We The People," and chanted athletically, "REA-GAN! REA-GAN! REA-GAN!" Another faction chanted back, "OL-LIE! OL-LIE! OL-LIE!"

For many the presence of their president and other details of the ceremony were a matter of blind faith. Both the official ceremony and the entertainment that preceded it were marred by inaudibility, a confusing, cluttered stage area and a security wall that obscured the president and other dignitaries from general view.

As former chief justice Warren E. Burger, chairman of the Commission on the Bicentennial, began to read the preamble to the Constitution, the loudspeakers carrying his words to the section reserved for the diplomatic corps and other dignitaries lost amplification and left the murmurs and throat clearings of the audience more audible than Burger's recitation.

A veteran government public relations official said he was "mortified" by the ceremony, most of which the crowd on the West Lawn was unable to see. "A lot of people left in sheer disgust," said the official who asked not to be identified. "My God, the stage was facing the other way."

Heat and humidity, as well as the production problems, took their toll on some members of the audience.

According to U.S. Capitol Police spokesman Dan Nichols, 14 people became ill and were taken to area hospitals: 13 of them for heat-related problems and one, he said, for a possible heart attack.

Nichols said Red Cross attendants treated 20 to 30 people on the Capitol grounds for heat-related symptoms.

In addition to schoolchildren and tourists, the occasion brought out a large number of federal workers who were granted a special 90-minute leave to coincide with the Capitol and National Archives activities.

Officials had hoped to see a turnout of at least 10 percent of federal workers from offices in the vicinity, and thousands of passes for priority seating and a standing area were distributed to various government agencies. According to agency supervisors, virtually all of the passes were snapped up and most believed that their employes took advantage of the "minivacation" for its intended purpose, and not just as a long lunch hour.

Deborah Prochaska, an aide at the U.S. Department of Labor, was responsible for handing out 1,200 priority passes there. "The enthusiasm really developed," Prochaska said. "I was still responding to requests for tickets this morning."

At the National Archives, where bicentennial festivities have been under way since Sunday, office workers and tourists hoping to catch a glimpse of the original four-page document stood in a line that snaked down the front stairs.

As they waited, they were able to listen to the speakers from the Capitol, and when Reagan began the Pledge of Allegiance, a few dozen people in the line chimed in.

Seeing the results of "the miracle in Philadelphia" was particularly meaningful to Dawn Marie Warfle, a former government teacher who now works for the International City Management Association. She said she believes the Constitution is "a flexible document that has helped us survive as a nation."

Barbara Brooks-Atkinson, national director of Reading Is Fundamental Inc., said she had planned to bring her three young grandchildren to see the Constitution, but they could not get out of school. She decided to come anyway, "to participate in history."

"I hope by the time my grandsons grow up, the Constitution will mean more to them than it has meant to some of us," said Brooks Atkinson, 58. She said the Supreme Court's 1954 school desegregation ruling led to numerous positive changes for blacks, but the pace of those changes has slowed considerably in recent years.

Harrison and Felix Lin, 19-year-old twins from St. Paul, Minn., were visiting Washington with their parents and decided yesterday might be their only chance to see the Constitution.

"My mom and dad came here from Taiwan, and they're really concerned about the conditions there," said Harrison Lin. "They tell us we're lucky to have so many freedoms here."

Staff writers Sandra R. Gregg, Ed Bruske and Bill McAllister contributed to this report.