Jim Gordon Liddy, the 25-year-old son of Watergate figure G. Gordon Liddy, has entered his first pentathlon, at the U.S. Olympic Festival in Houston. The Navy ensign will test his equestrian, shooting, fencing, swimming and running skills in the event.

Talking about his father, Liddy said he wasn't sure he would have gone along with the 1972 Watergate break-in, except if it had been for national security reasons. He said his family didn't talk about the crime while his father was in prison. "It was something I knew I wasn't supposed to know," he said. "But I knew my dad was not an evil man, not Darth Vader. He's my dad." Out and About

President Reagan has named Pam Shriver, who recently won her fifth women's doubles championship at Wimbledon with Martina Navratilova, to the President's Council on Physical Fitness and Sports. The 24-year-old tennis star from Lutherville, Md., will become the youngest member of the council, which is chaired by former Redskins coach George Allen . . .

The U.S. Air Force has renamed its Sunnyvale Air Force Station in Sunnyvale, Calif., the Onizuka Air Force Station, in honor of Lt. Col. Ellison S. Onizuka, who died Jan. 28 in the Challenger space shuttle explosion . . .

Actor James Dean has been dead now for 30 years and his fans still feel he hasn't had sufficient recognition. A group of them has placed an advertisement in The Hollywood Reporter inviting contributions for a $200,000 James Dean memorial to be constructed at the Hollywood Memorial Park Cemetery. Dean, who starred in only three movies, is buried in his home state of Indiana. The planned memorial would be Hollywood kitsch: a bronze statue, seven feet high, finished in 23-karat gold leaf. It will stand on a black granite base, with Dean's name etched in gold. Three black granite curved columns will form a backdrop, each column symbolizing one of his films. It will be interesting to see how much money flows in for this project . . .

Duke Zeibert, a figure of Washington's reigning restaurant royalty, is at Washington Hospital Center recovering from heart bypass surgery. Zeibert was operated on Friday and will remain in intensive care until tomorrow. He will be in the hospital another week, his son Randy Zeibert, who runs the restaurant with his father, said yesterday. But he should be back dishing up pickles and onion rolls in another six weeks . . .

Author's notes: Mark Perry, editor of The Veteran, the monthly newspaper of the Vietnam Veterans of America, has signed a contract with Houghton Mifflin for $35,000 for a book on the Joint Chiefs of Staff with the working title "Four Stars." It will cover the relationship of the joint chiefs to the national security apparatus, beginning in 1967 when they almost resigned after President Johnson refused to call up the reserves to serve in Vietnam . . . Former Washingtonian Meryle Secrest's biography "Salvador Dali" will be published by Dutton in October. The Sunday Times of London has purchased reprint rights to the book, described as the first full-scale biography of the surrealist artist. Secrest has also written "Being Bernard Berenson" and "Kenneth Clark" . . .Wolf Blitzer, Washington correspondent for The Jerusalem Post, has signed a contract with Simon and Schuster for a book on "American Jews and Israel." Broadcast station owner and television producer Alex Sheftel, who was the agent on the book, said he hopes to develop it into a television special . . . Most authors fly to cities across the nation promoting their latest efforts. Former CBS News anchor Walter Cronkite has a different plan. On tour for "North by Northeast," a book of paintings of marine artist Ray Ellis for which he wrote the accompanying text, Cronkite will be attending autographing parties with Ellis in the Maine cities of Bar Harbor, Camden and Portland, as well as in Martha's Vineyard and Boston, and he will get to those parties under sail on his 42-foot sailboat Wjntjel. And if the wind and weather holds, he might be on time . . .