The entire Kelly family -- ive of them -- were at the National Shrine yesterday, celebrating Christmas by waiting tables.

Timothy, Jr. who is 12, willingly -- even enthusiastically, according to his 18-year-old sister, Kristine -- left his brand new Atari game of "E.T." at home to join his parents and two sisters in the Shrine's cafeteria, where more than 800 persons showed up for the Seventh Annual Christmas Dinner for the Poor and Lonely. While his parents and sisters served, Timothy wrapped silverware in paper napkins.

The Kellys were among 400 volunteers serving free Christmas dinners to the hungry and homeless. Other volunteers at the Shrine included Joseph McGowan, a retired schoolteacher, who came with his wife to volunteer, and Terry O'Driscoll, also with his wife, who left his three grown children at home cooking dinner. "We're liable to go home and find the kitchen all in smoke," he smiled, not seeming too worried at the prospect.

The Shrine menu consisted of sliced turkey, dressing, cranberry sauce, mashed potatoes with gravy, green peas, rolls with butter, pumpkin pie or cake, coffee, tea or soda. The Marriott Corporation, which operates the cafeteria in the Shrine, at 4th Street and Michigan Avenue NE, donated the food. Several Marriott executives and their families were on hand as volunteers, dishing out meals and waiting tables.

"It's neat that the people who come here can have a nice Christmas," explained "almost 16"-year-old Michelle Kelly, when asked what she enjoyed about the day.

Michelle's mother, Lynn, said she was sorry only that more opportunities to volunteer weren't available. "I think it would be nice if there were more places to volunteer," she said. "We try. Every time we find a place to volunteer, we do."

Around the Kellys, eating or waiting to be served, men and women of all ages appeared to be enjoying themselves. Four single women from Silver Spring -- Edith Goldberg, 74; Esther Simon, 81; Dora Schuman, 80; and Rose Leibowitz, 79 -- confessed that they were, in fact, Jewish but that they appreciated the opportunity to get out for the day.

They had come to the Shrine on a specially-provided bus along with 16 other persons from their apartment building at 1400 Fenwick Lane. "There's nothing to gripe about when people are good to you like this," Edith Goldberg said. As for the gift of a plastic Madonna and Child given as a gift to every guest, Goldberg said she intended "to give mine to a Catholic friend."

In the kitchen, chief chef Julius Watson was on a busman's holiday. He works in the same cafeteria five days a week as chief chef. Yesterday he was donating his time and considerable energy to making sure that everything came off all right. According to Watson's estimate, he had cooked 210 pounds of turkey, 100 pounds of dressing, 80 pounds of cranberry sauce, 200 dozen rolls, and 100 each pumpkin pies and cakes.

Besides the 860 meals served in the cafeteria, the Shrine sent out 200 box lunches to persons unable to get out and donated 175 meals to So Others May Eat. Watson said that this was his seventh year voluntarily overseeing preparations for the dinner. "I like it," he said, "but I'd rather be at home." He does, he said, because "It's doing something for people who aren't as fortunate as I am. Besides," he added, assuming a proprietary posture, "it's my kitchen. I don't want someone else running my kitchen."

By Watson's count, this year's turnout was bigger than last year when between 500 and 600 meals were served. This year, he said, preparations were made to feed about 1,500, although the number of meals served and sent out fell short of that.

Some of the leftovers were sent over to So Others May Eat, where food coordinator Willard Webster said they will be served today. Webster said S.O.M.E. served 250 persons breakfast yesterday and 390 lunch, which was "definitely more than last year." Usually, Webster said, S.O.M.E. serves fewer persons on Christmas than other days because so many places are offering free meals. "I was surprised we had so many this year," Webster said. "A lot of younger people."

Earlier in the day, several hundred volunteers participating in The Holiday Project distributed gifts at more than 50 hospitals, nursing homes and other institutions -- including Lorton Reformatory. The Project began on a relatively small scale in 1975, according to Len Arzt, who works at the Department of Energy, and has grown every year since.

"It's the greatest Christmas gift that I give to myself and everyone else," Arzt said.

According to B.J. Sobus, local chairman for the nationwide Project, more than $20,000 in gifts were distributed yesterday in the metropolitan area and by affiliated Projects in Virginia, West Virginia, Maryland and Delaware.