The appearances of President Carter and Sen. Edward M. Kennedy at the dedication saturday of the John F. Kennedy Memorial Library are being regarded, in both camps, as matters of some personal and political delicacy.

There is delicacy in the handling of the speeches that the two men will deliver at the ceremony in Boston. And there is delicacy in the question of the private family luncheon that will follow -- a question that comes down to: guess who's not coming to lunch?

By both sides, the speeches are being handled with care.

For Kennedy, there is personal trauma in the occasion, as his speech will be largely a discussion of his brother who sought and won the presidency only to be slain in office.

The senator's aides are saying only that Kennedy's speech is being written by the senator, even though they know that is not entirely the case.

In the White House, there is concern of a different sort. Presidential aides concede that Carter is receiving considerable help on his speech -- it is, after all, a politically awkward situation in that he will be paying tribute not only to a president, but a family that is openly challenging his right to another term as president.

"There is a great deal of delicacy to the speech," said one aide who has been involved in the process. "He wants to make sure he doesn't say anything that would detract from the dignity of the occasion."

White House planners say they had been keeping open a time period following the ceremony because they understood that there would be a private luncheon for family and friends in the library, and the president wanted to be available to attend, if that was the Kennedy family's wish.

But the president has not been invited to the private luncheon, according to a White House aide.

And so the president now plans to return to Washington immediately after the ceremony.

Kennedy's press secretary, Thomas Southwick, says that the plan calls for box lunches to be served to all of the guests, and that tents are being hoisted to serve as luncheon areas.

"the library explained to the White House that they would be serving box lunches and that the president would be welcome to stay," Southwick said. He explained that the Kennedy family, and probably a few friends, did not plan to eat their box lunches under the tents, saying: "The family members are going to go off into the library to eat their box lunches."

The president will not be joining the Kennedy family at its indoor box luncheon -- but apparently the senator will not either. For after asking Kennedy whether Carter was invited to the family lunch, Southwick said that the senator told him he would be passing up the box lunch in the library to attend the Harvard-Dartmouth football game.