Yuletide Lesson in Giving : * A child learns the spirit of the holiday by ‘playing Santa’ to a less fortunate girl. A wish list picked up at the post office is used for shopping.

How do you teach a 5-year-old whose Christmas stocking will overflow that there are children whose parents can’t afford a Christmas tree?

We thought that we’d try bringing home the spirit of giving by using the universal language of childhood--presents--and having our daughter “play Santa,” even though she isn’t sure she still believes in him. Gillian came home from kindergarten this fall and said, “Douglas doesn’t believe in Santa Claus. He says your parents fill the stockings.”

“What do you think?” I asked.

“I’m not sure,” she said. “I think it’s possible there’s a Santa Claus.” Later, she was overheard explaining to a 4-year-old how all the Santas in malls are “fake, because the real one is busy making toys at the North Pole.”

When I bring up the idea of going to the post office to pick out a letter written to Santa, to help him answer a needy child’s Christmas request, Gillian is bothered by one thought: Why can’t Santa get children everything they need?

Santa asks for help because these children need so many things, I say. Plus, these children are lucky if their parents can afford to buy a single gift.

Her jaw drops.

So we travel the 55 miles from our Agoura home to Santa Clarita and the regional post office that handles the letters for the Santa campaign. It is so far that my 2-year-old son thinks that we are going to the North Pole. “If Santa doesn’t have anything for us, will we come home? Will we see Santa?” he asks.

At the post office, we find the consumer affairs office in charge of the Santa letters, sit on the floor and read letter after letter aloud. “Santa, I believe in you,” say many of the letters from a local second-grade class, all with brightly crayoned illustrations and a teacher’s mark noting that this is a child who is truly needy. Letters penned in Spanish have English translations attached.

The letter we are looking for must be written by a girl (Gillian’s orders), so we pass over many of the requests from boys, who seem to be asking en masse for Power Rangers, which my daughter thinks is “some Ninja thing,” and bikes. Not all of the requests are TV-driven. Another woman who picks a letter while we are there chooses two brothers who ask for a Bible and clothes.

My favorite is a mother-daughter missive, which contains a one-line postscript from the girl’s mother: “Santa, for Christmas, I would like a job.”

But Gillian chooses a 4-year-old’s letter--clearly penned with a parent’s help in black marker--because she also asks for gifts for someone else. “I have been a good girl all year and so has my sister,” she writes, before listing her wants, and adding, “Santa for my sister she’s 1 year old and . . . she needs clothes.”

After we choose our letter, I sign a document that states I will use the letter only for charitable purposes. We are handed a form letter from Santa to include in our package, if we like. “Dear Elfkin,” it begins, “My faithful postman just arrived at the North Pole by snowmobile. He delivered a mailbag full of joy from girls and boys all over the world, and in particular, a letter from you!”

When the helpful postal employee starts to go on about the Santa program--you can answer a stack of letters to Santa with a form letter or be matched with someone by region--Gillian looks suspicious. The postal employee catches on and, with a jolly laugh, says to her, “That’s why the post office exists--to help Santa!”

At my daughter’s insistence, we go to fulfill the wish list the very next day. We cruise the aisles of Toys R Us as she reverentially holds the list. Something strange is happening--my children behave perfectly in a giant toy store. There are no “gimmes,” and my son stays in the shopping cart, even when we wander down the basketball aisle (No. 1 on his Christmas list). Instead, we earnestly debate what this child we have never met would really like.

We get her the top two toys on her list--a washing machine and dryer and a vacuum--a doll called Baby Giggles ‘n’ Go (No. 4 on the list, after the somewhat puzzling “deer”), some Barney sticker books (No. 7), a Barney purse, toy phone, some Christmas candy (not on the list, but Santa has to pull some surprises). At a nearby Marshall’s, Gillian earnestly searches the racks, and we agree on two outfits for the baby sister.

Still in the compulsive mode (OK, so it’s genetic), Gillian insists on wrapping the gifts that night. I try not to worry too much about creating perfect packages, allowing her to help with the wrapping and ribbons. “To a good girl. Love, Santa,” we write on a tag.

We make plans to deliver the gifts as a family, then change our minds and mail them. At first, we think that we’ll miss the payoff by not meeting the girls in person. Then we worry that we’ll have some awkward moments because strangers have swooped in to help this family have a better Christmas.

In one package, we enclose the letter from Santa provided by the post office, with a handwritten addition: “I decided to mail your packages because I was worried about getting there on time. Don’t worry though, I’ll still come by Christmas Eve. Merry Christmas. Love, St. Nick.”

The boxed packages sit in the living room long enough for one of Gillian’s schoolmates to ask who they are for.

“A needy child, someone who doesn’t have a lot of money, someone we don’t know,” I tell her.

“Does she have a little bit of money?” she asks.

“Yes, like three dimes and one nickel,” Gillian says with some authority.

Well, she didn’t get it exactly right. But it is Christmas and, instead of constantly revising her wish list, she has spent hours obsessing on another child’s holiday. It’s been a good lesson, one we are already planning to repeat next year.

And tomorrow morning, our wishes will be with a little girl from Sylmar who mailed a letter to “Santa, North Pole.”