President and Mrs. Reagan led an official delegation of mourners to Fairfax County yesterday for the funeral of Scott R. Meese, the 19-year-old son of White House counselor Edwin Meese.

Vice President Bush, at least nine members of the Cabinet and numerous White House aides were among the congregation that filled every pew in Emmanuel Lutheran Church in Vienna. Young Meese died late last Thursday in an auto accident.

"We're not here to cry or mourn, although there are tears," said the Rev. Benson M. Bartell, pastor of the church. "We are here to celebrate life, the life of a beautiful young person . . . who gave the Meese family so much."

Almost 500 people attended the 45-minute service, and traffic in Vienna was snarled for more than two hours as local residents gathered at curbside in 95-degree heat for a glimpse of the president.

Inside the church, the Reagans appeared misty-eyed as Bartell and the Rev. James Ford, chaplain of the U.S. Senate, recounted the young man's unflagging good humor and his dedication to church youth group activities. Scott's "was a life of enthusiasm, a life of giving, a life of service," said Ford. " . . . His faith didn't stop at the church step."

Following the service, the president returned to Washington by helicopter, while Mrs. Reagan, accompanied by White House Chief of Staff James A. Baker III, Deputy Chief of Staff Michael K. Deaver and National Security Adviser William P. Clark, visited the Meese home in McLean.

Friends of Scott Meese described him as a warm, friendly person who was as consumed with his love of people as he was with softball.

"He was a very fun person to be around," said John Chludzinski, a classmate at Princeton University. "He wasn't wild in any way. He was very kind. He always wanted to do nice things for people."

Police said that Meese, a sophomore divinity student at Princeton, was traveling at high speed shortly before midnight Thursday when he attempted to pass another car on a curve of the George Washington Memorial Parkway, just south of Rte. 123 in McLean, and lost control of his car.

His 1979 Volkswagen Dasher went more than 300 feet on the parkway's grassy median before crashing into a tree and bursting into flames. Police said they found no evidence that Meese had attempted to apply the brakes before impact, and estimated that he could have been driving at up to 80 miles an hour when his car left the road.