"Bid reasonably, but generously," says auctioneer John Walker Jenkins. But even a bargain price will benefit Washington, Virginia's child care center at its fundraising auction Saturday in Sperryville. Items offered include an TV interview about the subject of your choice on Channel 56's "Greenroom," five dogwood trees, a stereo receiver, a lamb, and handmade dolls.

Admission to the following activities is free unless otherwise noted.

"GRAND CANYON" MOVIE -- Friday at 3, Saturday and Sunday at 1 and 3, Watkins Nature Center, 301 Watkins Park Drive, Largo. 249-6202.

NATURE TRIVIA -- Friday, 8 to 9 p.m., Burke Lake Park amphitheater, 7315 Ox Rd., Fairfax Station. Families are invited to test their knowledge of the natural world. 451- 9588.

BEACH DRIVE CLOSINGS -- 7 a.m. Every Saturday through 7 p.m. every Sunday, Beach Drive, Upper Rock Creek Park. Bicyclists, joggers and hikers are free to travel without motorized traffic. 426-6832.

BIRD AND BREAKFAST -- Saturday, 8 to 9:30 a.m., Hidden Pond Nature Center, 8510 Greeley Blvd., Springfield. Have continental breakfast, then search for summer resident birds. $2. Reservations required. 451-9588.

TIME AND CHANGE -- Saturday, 10 to noon, Walney Visitor Center, Ellanor C. Lawrence Park, 66W to left on Sully Road (Rte. 28), right on Walney Road, one mile to Visitors Center on left. A naturalist/historian will talk about time and change in geology, history and people's lives. Reservations required. 631- 0013.

BENEFIT AUCTION -- Saturday, 10 to 2, Sperryville Antique Market, off Rte. 211, Sperryville. Auctioning off tours, airline tickets, weekend trips, dinner for two, museum memberships, sports tickets, a brass crib, a bushel of apples, bicycles, dolls, a wooden sled and more. Proceeds go to the Child Care and Learning Center of Washington, Va. 703/675-3846.

DAYLILY SHOW -- Saturday, 1 to 5, Tysons Corner Marriott Hotel ballroom, 8028 Leesburg Pike, Vienna. 23rd annual show sponsored by the National Capital Daylily Club. 301/589-4804.

NATIVE VIRGINIA SNAKES -- Saturday, 7 to 8 p.m., Huntley Meadows Park Visitor Center, Harrison Lane and Lockheed Boulevard, Hybla Valley. A naturalist shows you a live black rat snake and an eastern king snake and teaches about their feeding habits. 768-2525.

CHESAPEAKE BAY, BARREN? BEAUTY? -- Saturday, 8:30 to 9:30 p.m., Lake Fairfax Park outdoor amphitheater, 1400 Lake Fairfax Dr., Reston. Slide/tape presentation and discussion about the endangered Bay, its importance and your possible help. $3.50 per car for non-Fairfax residents. 759-3211.

TORNADO WATCH -- Saturday, 8:30 to 9:30 p.m., Burke Lake Park amphitheater, 7315 Ox Rd., Fairfax Station. Slide show about severe weather, the causes of hurricanes, tornadoes and hail storms. 451-9588.

BALLROOM DANCING -- Every Saturday, 9 to midnight, Star-Lite Dance Studio, 6333 South Kings Highway, Alexandria. $4 for non- members. 370-2797.

WOODCARVING LESSONS -- Sunday, noon to 4, Colvin Run Mill Park, Rte. 7W, 5 miles past Tysons Corner to the mill entrance on the right. Northern Virginia Carvers share tools and expertise of 19th-century carpenters and cabinetmakers. Fee for wood used. 759- 2771.

CRAFTS AND MUSIC DAY -- Sunday, noon to 5, Glen Echo Park, Glen Echo. Informal presentations on techniques and processes involved in displays of toys, jewelry, basketry, prints, watercolors, country music and dance. 492-6282.

RECYCLING FOR THE BIRDS -- Sunday, 1 to 3, meet at the ice cream parlor, Burke Lake Park, 7315 Ox Rd., Fairfax Station. How to turn milk cartons, tin cans and more into birdfeeders and houses. 451-9588.

HOMEMADE HERBAL VINEGARS -- Sunday, 1 to 4, Sully Plantation, on Sully Road, Chantilly. How to make the now gourmet vinegars of tarragon, basil, rosemary and thyme. $2 for adults, $1 for children and senior citizens includes a tour of the historic house. 437-1794.

LIVING LEGENDS -- Sunday at 1:30, U.S. National Arboretum, Administration Building, 3501 New York Ave. NE. Program on how to select elite trees, breed new shrubs, save/store seeds, create a hybrid plant. 475- 4857.

HIKE AT FERRY HILL PLACE -- Sunday at 2, Ferry Hill Place, Park Headquarters, Md. Rte. 34, Sharpsburg. Hike includes history of the canal and stops at the Potowmack Co., James Rumsey's steamboat, Blackford Plantation and the former home of Confederate Officer Henry Kyd Douglas. 301/739-6179.

EXPLORING BIRD BEHAVIOR -- Sunday, 7 to 8:30 p.m., Huntley Meadows Park, Harrison Lane and Lockheed Boulevard, Hybla Valley. Visit a wetland "nursery" and learn how to spot nests, nestlings and fledglings. 768-2525.