It may be for security or simply for convenience, but for the first time in recent memory, the sentimental smell of Christmas turkey will permeate both the White House and the vice president's home on Dec. 25.

To the relief of dozens of Secret Service agents, the White House staff and the Washington press corps, both the Reagans and the Bushes will celebrate Christmas in Washington, though not together.

And many of Washington's cave dwellers -- those who generally slide down Alpine slopes or sun in Puerto Rico during the holidays -- also will be here this year.

Joining the Reagans at the upstairs family quarters for the day will be their son, Ron, and his wife, Doria; daughter Patti Davis; the first lady's brother, Dr. Richard Davis, his wife, Patricia, and their two children; and close friends Charles and Mary Jane Wick and the Wicks' five children.

"Well, our house is for sale in California, and the only other place to have Christmas would be the ranch," the president said recently, "and since a lot of our family is in the East now, we thought the thing to do would be to have Christmas here.

"The Wicks are coming, and you know it used to be a tradition for us to spend every Christmas with them," he said. "We'd sing Christmas carols, and they would have a Santa Claus and everything. It'll be great fun having everyone together here."

Dinner, set for 5:30, will include turkey with chestnut stuffing, candied sweet potatoes with marshmallow and monkey bread, which is an egg bread rolled in butter and baked. Dessert will be a frozen "Christmas log" with pistachio filling.

For the Bushes -- who leave for Texas the day after Christmas -- the recently hyped-up security precautions helped them decide where to spend their holiday.

"The decision was to stay here so . . . all the Secret Service wouldn't have to leave their families," Barbara Bush told reporters at a recent Christmas tea. "Why would you ruin Christmas for agents and staff by having everyone traveling the whole time?"

Twice annually -- during Christmas week and during the sticky summer months -- Washington traditionally becomes eerily empty. At this time of year, Senate and House members exit en masse, jamming the airports and train station on Dec. 23. And presidents often have headed toward family retreats. For the Kennedys, it was the family mansion in Palm Beach. The Johnsons went to the Texas ranch. The Fords never let the rigors of the White House take them from their ritual ski holiday at Vail. Old-line Washingtonians head for the mountains. The town closes down.

"I suspect that most presidents leave for Christmas because they consider the White House their temporary home and their real home somewhere else," said former Ford spokesman Ron Nessen. "In the Fords' case, Christmas and Easter had always been a time to get the entire family together and they had always done that at Vail."

For all those traveling with the Fords, Vail was a delightful vacation compared with the uneventful nights many have spent at the Santa Barbara Sheraton when the Reagans go to their ranch.

So while the first family's decision to stay here might curtail staff travel during this season, it does allow them to spend the holidays with their families, and for many of the Californians it affords the opportunity to spend their first holiday season in the blustery East.

Here is what some Reagan Californians and Washingtonians will be doing next week:

* Departing Protocol Chief Leonore Annenberg and her husband, Walter, are spending Christmas at their 200-acre Palm Springs estate. And, for the 14th consecutive year, they will entertain the Reagans there on New Year's Eve. This year's party has been expanded from the traditionally small gathering of Annenberg and Reagan intimates, to include about 90 friends and administration officials.

* "We're staying right here," said Peter McCoy, assistant secretary of commerce for tourism. "I got home late from a reception the other night and found Kacey and the children waiting on the doorstep for me to go out and get a tree. We wanted to spend our first Christmas in Washington, and maybe it will even snow."

* Presidential counselor Edwin Meese, deputy chief of staff Michael Deaver, presidential assistant E. Pendleton James and deputy assistant to the president Joseph Canzeri and their families are all venturing together to colonial Williamsburg for Christmas. "I thought it would be nice for my son," said Canzeri. "It's so American, and it'll be pretty. We're all going to take part in all the activities there."

* Mayor Marion Barry, his wife, Effi, and son Christopher are planning a "warm vacation somewhere in the country" during the New Year's weekend, said a spokesman for the mayor, but "he'd rather not say where he'll be."

* Attorney General and Mrs. William French Smith are leaving for California this week to spend both Christmas and New Year's. "I'm going because I worry about my mother. She's 87, and I hate to leave her alone," said Jean Smith. "Actually, I wouldn't mind spending Christmas here. The weather will be warmer in California, but more Christmasy here."

* Tom and Joan Braden, whose large family inspired the book "Eight Is Enough," have opted to keep the troops home this year. "For years we figured that taking everyone to Puerto Rico for a week would cost the same as having Christmas here when you figure on the tree and presents for eight kids," said Joan Braden. "But now that they have all gotten older, everyone is anxious to spend Christmas at home." Among those expected at the Bradens' on Christmas Eve are Henry and Nancy Kissinger, David and Susan Brinkley and Evangeline Bruce.

* "We're going to Denver to visit Jim's family," said Leilani Watt, wife of Interior Secretary James Watt. "It will be our first real vacation since he took office."

* Luther Hodges, chairman and chief executive officer of the National Bank of Washington, is traveling south. "I'll spend Christmas Day with Eastern Airlines on my way to Jamaica," says Hodges. "I plan to sun, play tennis and invigorate myself."

* Transportation Secretary Drew Lewis and his wife, Marilyn, will be going to their farm in Pennsylvania for Christmas with the family. "We used to take the kids and go skiing, but there's no time for that sort of thing now," says Marilyn Lewis. "Quite frankly, I live in and out of a suitcase all year and I welcome the time to just relax and be in one place. For New Year's, I hope to be sitting in front of a fire reading a book."

* Mineral heiress Sophie Engelhard and her boyfriend, Redskins offensive tackle George Starke, are planning a Christmas vacation on Bequia Island in the Caribbean. "My boyfriend has a house there," says Engelhard. "He'll kill me for telling you that."

* "I plan to hunt and relax in Middleburg over Christmas," says Pamela Harriman, who, with her husband, Averell, and some friends, will spend the holiday at their Virginia farm. "I get the Churchill grandchildren every other year, and this isn't my year, so I'm a little sad as only a grandmother would be. But we'll have fun with our friends and pray for peace and prosperity in the New Year."

* "We're all ski freaks and we go to Aspen every year," says Jessica Catto, publisher of the Washington Journalism Review and wife of Henry, assistant secretary of defense for public affairs. "I just love being in the mountains with all the white snow. For New Year's, if I'm lucky, I'll be home by 10."

* Del. Walter Fauntroy (D-D.C.) will spend Christmas Day with his family but be working during much of the rest of the holidays. As chairman of the House subcommittee on domestic monetary policy, he will travel to Indianapolis and Chicago for hearings.

* "Honey, you're crazy if you think I'm going to tell you what I'm doing over Christmas," said one Washington socialite. "Why not just take an ad out and invite the burglars to dinner?"