CHILDREN’S ACTIVITIES : Christmas is old news--now it’s time to get out and have some fun.

Now that the gifts have been unwrapped and the children are in high gear, many parents begin longing for the start of school again, and a return to relative normalcy.

Short of that, it may be time to simply get out of the house for a while. But what is there to do that is cheap, close to home and guaranteed to burn off a little of that excess kid energy?

For a start, there’s the Cabrillo Marine Museum in San Pedro, where toddlers to teen-agers can learn about the many marine creatures living in the ocean and tidal regions virtually in our back yard. They can even reach out and touch a slimy sea hare or a prickly sea urchin in the museum’s outdoor Tide Pool Touch Tank.

At least 30 aquariums filled with fish, sea plants, crustaceans and other bottom dwellers are grouped by ecological zone, including mud flats, sandy and rocky shores, the kelp forest and the open ocean. Other, action-packed exhibits demonstrate the effects of wave action and the rising and falling tides on marine life forms.

There are life-size models of shore birds, seals and sea otters, and sharks. Maps of whale migration routes fill entire walls, and whale skeletons are displayed with signs that read, ‘Please touch.’ Docents are on hand to answer questions, and slide shows about whales, sharks and other marine life are shown at various times of the day.

The museum is open through Jan. 3 (except Mondays and Christmas Day) from 10 a.m. to 5 p.m., including New Year’s Day. Admission is free, though there is a $5.50 parking fee.

A limited display of marine plants and animals is available at the Manhattan Beach Pier’s newly opened roundhouse, open from 10 a.m. to 5 p.m. Saturdays and Sundays. Admission is free. Beach area meter parking is available nearby; bring quarters.

For those whose tastes in wildlife are more land based, Hopkins Wilderness Park in Redondo Beach could be the ticket. In this 11-acre camping and nature study area, hiking trails wind through forests and meadows. Visitors can find native trees such as California redwood and bay, cottonwood and eucalyptus, as well as non-indigenous varieties like Japanese black pine and Brazilian pear. This vegetation provides habitats for a wide range of animal species, from butterflies and other insects to lizards, gophers and tree frogs.

A variety of birds can also be seen, including hummingbirds, hawks, songbirds and occasional migrating herons. Park hours are 10 a.m. to 4:30 p.m. daily except Wednesdays and New Year’s Day. Admission and parking are free.

Railroad buffs might enjoy a visit to the Lomita Railroad Museum. Kids of all ages enjoy climbing on, in and through an authentic 1902 locomotive and 1910 caboose located outside the museum. For a dime they can activate the train’s wheels--one of few amusements available these days for that kind of price.

Inside they will find photographs, artifacts, and other railroad lore, along with an old-time train bell labeled “do not ring,” instructions most young visitors ignore. The museum is open from 10 a.m. to 5 p.m. Wednesday through Sunday, including New Year’s Day. Admission is $1 for adults and 50 cents for children. Parking is free.

Other children, particularly those interested in whale watching, might find the Point Vicente Interpretive Center at the south end of the Palos Verdes Peninsula to their liking. Whale watching is now under way at this official whale census location, and docents are on hand to answer questions and help identify offshore marine life.

Gray whales, dolphins, seals and sea lions are seen most frequently, though killer and sperm whales have also been observed from the outdoor, cliff-side viewing areas. Because whales surface to breathe, or blow, every one to six minutes, their passing is readily visible. Coin-operated telescopes are available (bring quarters), or visitors may use their own binoculars. The center has a few pairs to loan, but they are in constant use at this time of year. Warm clothing is advisable, even in good weather, since the strong ocean breezes can be chilly at Point Vicente.

Inside the interpretive center is information about whale migration and whaling, along with a life-size model of an infant gray whale--about 15 feet long. There is also an exhibit of American Indian artifacts found on the Palos Verdes Peninsula. The center is open from noon to 5 p.m. daily except Tuesdays and New Year’s Day. Admission is $1 for children and senior citizens, $2 for adults, with free parking.

A pleasant outing for parents of very young children might be the South Coast Botanic Gardens, which cover 87 acres of what was once a landfill. Trivia buffs will note that it is said to contain more than 3.5 million tons of trash. Though most of the park’s exhibits are adult-oriented, there is a man-made lake inhabited by koi and box turtles. Ducks and other waterfowl also gather there, and small children can feed them crusts of bread until they tire. Hint: bring lots. The gift shop also sells bags of corn for feeding.

The gardens also provide a delightful quiet break for parents. A stroll among the park’s many species of fragrant roses, eucalyptus and evergreens, flowering coral trees, herbs and a variety of hanging baskets in bloom is bound to be a sure cure for frazzled nerves. Hours are 9 a.m. to 5 p.m. daily. Admission is $3; children under 5 are free.

Cabrillo Marine Museum: 3270 Stephen White Drive (at Cabrillo Beach). 10 a.m. to 5 p.m. (except Mondays and Christmas). Open New Year’s Day. Free admission; $5.50 for parking. (310) 548-7562.

Hopkins Wilderness Park: 1102 Camino Real, Redondo Beach. 10 a.m. to 4:30 p.m., except Wednesdays and New Year’s Day. Free. (310) 318-0668.

Lomita Railroad Museum: 250th Street at Woodward Avenue, Lomita. 10 a.m. to 5 p.m. Wednesday through Sunday, including New Year’s Day. $1, children 50 cents. (310) 326-6255.

Point Vicente Interpretive Center: 31501 Palos Verdes Drive West (just west of Hawthorne Boulevard), Rancho Palos Verdes. $2 adults, $1 children and senior citizens. (310) 377-5370.

Roundhouse Marine Exhibit: Manhattan Beach Pier. 10 a.m. to 5 p.m. Saturday and Sunday. Free. (310) 379-8117.

South Coast Botanic Gardens: 26300 Crenshaw Blvd., Rolling Hills Estates. 9 a.m. to 5 p.m. daily. $3 adults, $1.50 for senior citizens and students with identification, 75 cents for children 5 to 12 and free for youngsters under 5. (310) 544-6815.