Bolstered by the first upward movement in weeks in their canvassing results, the backers of Sen. Edward M. Kennedy today launched an advertising campaign aimed at improving his personal image among voters in next Tuesday's New Hampshire primary.

The new radio and television ads feature the senator's mother, Mrs. Rose Kennedy, and his sister-in-law, Mrs. Ethel Kennedy, talking about how he held the family together with his "compassion" and "commitment" when his brothers were killed.

The TV ads show him playing on the beach with children of the Kennedy family and talking with family members about his concern for the elderly and the poor.

The new ads, according to Kennedy's New Hampshire political director Joanne Symons, are designed to focus on his "positive personal characteristics" and to offset criticism of his personal life.

"People needed to be reminded and reassured that he is a person of compassion and caring and responsibility," Symons said -- implicity acknowledging what journalists and poll-takers have found to be widespread doubts about Kennedy's character, stemming from the fatal accident at Chappaquiddick and his seperation in recent years from his wife, Joan.

Kennedy's new ad campaign was carried over in his stumping here today, his 48th birthday. He was surounded by family members as he moved from a senior citizen's center to a high school gymnasium to a number of house parties, all combining the elements of a political rally with a birthday celebration.

The Carter campaign also has produced new TV and radio commercials for the final days of the New Hampshire campaign, and some of them are thinly veiled attacks on the very characteristics that Kennedy is now trying to promote -- the senator's personal character.

"A man brings two things to a presidential campaign," intones an announcer at the beginning of the radio version of a new Carter ad, "he brings his record, and he brings himself . . . In the voting booth, the voter must weigh both record and character before deciding. Often it's not easy, and the voter ends up asking. 'Is this the person I really want in the White House for the next four years?' . . . Mr. Carter himself is a straightforward, unassuming family man. People respect his integrity. . ."

Rose Kennedy reminded the elderly that her youngest son had been at her side when three of his brothers "met their deaths in unexpected and tragic ways." Kennedy's children, Cara, Teddy Jr. and Patrick, told audiences that, in Patrick's words: "The greatest present you could give him would be happy returns on Tuesday."

Kennedy is a decided underdog in his first primary contest with President Carter, but Symons told reporters today that call-backs to undecided Democrats have shown "an encouraging pickup" in the proportion moving to Kennedy."

Chris Brown, Carter's New England campaign director, indicated that similar results are being obtained in the Carter canvas.

"Very seldom," Brown said in Concord, "do the undecided break for the front-runner. My guess is that two-thirds to three-fourths of those who were undecided at the beginning of this week and who end up voting will go to somebody other than the president -- either Kennedy or Brown [California Gov. Edmund G. (Jerry) Brown, Jr.]."

The shift in the media campaign takes Kennedy almost entirely out of the posture of attacking the policies of the Carter administration -- an attack that some published polls have suggested has rebounded against him.

In his major appearance today, at Manchester West High School, Kennedy used most of his speech to criticize the "single issue groups," which he said, "distort and disrupt the political process."

Kennedy has been the target of a large-scale radio and newspaper advertising campaign by sportsmen's and gun-owners' groups opposed to his proposed legislation, which would ban the small handguns known as "Saturday night specials."