President Reagan's wife, Nancy, and his four children rallied at his bedside in George Washington University Hospital yesterday where he was reported in high spirits and, as one of them said later, characteristically cracking jokes.

However, a little later when the president learned from White House physician Daniel Ruge about the serious nature of his press secretary James Brady's wound, his "eyes welled up with tears," according to his chief of staff James Baker. The first lady was present and said that Brady had not been expected to live on Monday night.

"Oh dear," the president is reported to have said, "Let us pray."

Yesterday he was also told that Secret Service agent Timothy J. McCarthy and District policeman Thomas K. Delahanty were out of danger.

"That means four bullets hit," the president said. "Oh Lord."

The president's first visitors of the day were the first lady with daughter Patti, 28, and son Ronald Prescott Reagan, 23, and his wife, Doria. Later, Maureen Reagan, 40, and her brother Michael, 35, the president's children by his first marriage to actress Jane Wyman, paid a separate visit to their father's bedside.

Afterward, Ron Reagan expressed "relief that my father is alive and well" and added that he also felt "pride in the way he acquitted himself." His sister Patti said she felt "very reassured and glad" after seeing her father. "I'm grateful he's alive and strong."

The first lady and Patti Reagan dropped in to see McCarthy and his wife to thank the Secret Service agent for saving the president's life. They also paid a visit to Sarah Brady, whose husband's condition was said to be much improved following surgery for a gunshot wound in the head.

Maureen Reagan and her fiance, Dennis Revell, and Michael Reagan and his wife, Colleen, went directly from seeing the president to Washington Hospital Center to visit District police officer Delahanty.

Apparently reassured of their father's rapidly improving condition, all of the Reagan children left Washington later in the day.

Ron Reagan and his wife had flown here Monday night from Lincoln, Neb., where he was scheduled to appear with the Joffrey II ballet. They spent the night at the White House with his mother, whom a friend described as "exhausted but calm."

Early yesterday morning Patti, Maureen and her fiance and Michael and his wife arrived here after an overnight flight aboard an Air Force jet from California which had been sent for them.

But for all of them, behind the smiles of reunion was the reality of the threat that has hung over their heads ever since Ronald Reagan entered politics and especially since he was elected president last fall.

In her autobiography "Nancy", the first lady wrote: "The families of men in power live in a fishbowl. Some of the pressures placed on your man press you, too, and you have to be strong to stand them. I had to learn to live with the thought and possibility of danger. But you take all the precautions you can, and then put faith in God and go about your daily life. If you don't, you can't function."

Twice before, the Reagans had faced the threat of assassination. In 1968, when Reagan was governor of California and a favorite-son candidate for president, Secret Service agents scared away would-be assassins who tossed a Molotov cocktail beneath the Reagans' window.

Another time in Miami, after Reagan announced his candidacy for president in 1976, Secret Service agents carried him to safety fearing that the gun a young man was brandishing in a crowd was real. "It turned out to be a toy. But it certainly looked real," Nancy Reagan wrote in her book.

The Reagans' daughter Patti disagrees with her father's opposition to gun control. In the April issue of McCall's magazine, she is quoted as telling an interviewer:

"I know that his reasoning is: If a criminal wants to get a gun, he's going to get one, gun control or not. But I don't think that's necessarily true. The climate that has evolved in this country is crazy; people are getting robbed, raped, shot for no reason."

A longtime Reagan friend, Los Angeles industrialist Armand Deutsch, reached yesterday by telephone, said he had always "differed" with the president on gun control "and I suppose everyone will speculate on whether what has happened will change his position on it."

Another friend, Betsy Bloomingdale, whose husband, Alfred, founded the Diner's Club and is mentioned as Reagan's likely nominee as ambassador to Great Britain, broke down in tears on the phone when she started to describe how "devastated" she felt over the assassination attempt.

"I'm so grateful he's all right, but poor Mr. Brady and the others. Oh my God," she said, her voice cracking, "How do you live like this?I heard last night that Sirhan Sirhan [Robert F. Kennedy's convicted assassin] could be paroled in three years. What's the matter with this country?"

Another friend of the Reagans said Nancy Reagan would "never panic or make it hard for the president . . . he's such a happy man doing what he is doing, happy and content." But at the same time, said the friend, "no one ever reconciles himself or herself" to the dangers of public life.