WHERE TO PET THEM For a free visit, plan to arrive after 10 and leave before 4. (These are feeding times, and the animals won't go willingly into the barn to be fed if there's a crowd.) To get to Chester Farms, take U.S. 15 in Virginia to four miles south of Gordonsville. Then follow Route 22 two miles west, to the community of Boswell's Tavern. (Call 703/832-3326.) The Wool Fair and Sheep Dog Trials, May 5 and 6, will be from 9 to 6. Admission is $2 for adults, $1 for children under 12, and free for children under 4. Unlimited hayrides.

Queen of the sheep fold, a svelte llama dubbed "Crumpet" draws us with her bright, liquidy, black-molasses eyes.

Her pacing style fools us into thinking there's more than one of her - in and out, out and in the back of three empty stalls; back and forth, and forth and back along a short fence line.

If you're patient and move in slow motion, she may allow you to pat her. And, with her indulgence, you may feel the velveteen softness of her muzzle brush against your cheek.

Just for that, it's worth loading up the car with children and driving to Chester Farms, an unpretentious, private-yet-public sheep farm in Virginia.

It's a three to four-hour drive south to rich farming and timber land in Louisa County. The last hour's gentle cruise along rolling farmland and wooded byways leads to the outer, open gate. Then, after a rumbling, rambling country mile through dogwood-laced woods, you're there - in the pasture near the white clapboard colonial farm-house by the weather-worn sheds of Chester Farms.

On a week day you may at first feel like an intruder as you alight, even after assurances that it's all right to go unannounced.

But the gate is open. The sign does say, "Welcome to Chester Farms." And no one comes out to ask, "What do you want?" or "What are you doing here?"

No one bothers you. You and your children are free to look, to pat, to marvel at farm life - particularly new-born life.

"Ohhh . . . aren't they cute," exclaims the five year old who sees the lambs nursing.

Most of all at Chester Farms there are sheep - five hundred head, give or take a lamb. At this time of year the count can change dramatically overnight. On our early spring visit there were four sets of twins less than a week old in the fold. Another pair appeared on the scene within the hour, much to the delight of five excited children.

There are goats, too, at Chester Farms. Mohair and dairy goats, with 22 ready for kidding on the most recent visit.

Inexpensive to keep and profitable, dairy goats, we're told, provide supplemental milk to ewe's milk, as well as making good milk for people to drink.

"The tender meat of kid," we hear aside from our kids, "is prized even more than lamb."

Even Crumpet has commercial value. A cousin to the camel, the llama has wool that is very soft, very fine - and very expensive. When it can be bought, it sells by the ounce like some rare Parisian perfume.

You can visit the farm any day, but the first weekend in May is special. Francis and Diane Chester will host their ninth annual Wool Fair. Upwards of 3,000 visitors come to see the annual sheep-shearing.

Where there are sheep, there are sheep dogs, and the International Sheep Dog Trials will be held there the same weekend. Close to 50 handlers and their dogs from throughout the United States and Canada compete in an upper pasture of Chester Farms. Using only hand signals and whistles, handlers take turns directing their dogs to herd five sheep through a 12-minute obstacle course. Swiftly and surely they bring home the sheep.

Though it didn't start out big, the first year of the fair, Chester says, "We got the biggest surprise. They came from everywhere. We never expected such a crowd.We had to borrow trucks and wagons for hayrides. Our friends pitched in and helped."

This year, costumed Virginia craftspeople will be there, spinners will be spinning, weavers weaving, dyers dyeing. It's what Chester calls a "sheep to shawl spinoff." Judging will be May 6 at 4, followed by an auction of the creations.

Lamb (Chester's own) will be served. CAPTION: Picture, EWE AND LAMBS ON A FARM IN SPRING, AS SHEARING TIME NEARS.