It's logical that given the opportunity to select a date for his farewell party, House Speaker Tip O'Neill would pick March 17 -- St. Patrick's Day. The $1,000-a-plate black-tie dinner in the Washington Hilton will benefit the Thomas P. (Tip) O'Neill Scholarship Fund at his alma mater, Boston College. There will be a series of farewells for the powerful and popular speaker, but this is one he has endorsed. In the four days since the invitations were mailed, some $700,000 worth of tickets have been purchased.

Former president Gerald Ford, who served so many years in Congress with O'Neill, is the honorary chairman of the evening along with former president Jimmy Carter. Ford is expected to attend, Carter is not. House Minority Leader Robert H. Michel is going to sing. Other scheduled speakers include O'Neill's predecessor as speaker, Carl Albert, entertainer Bob Hope, former Reagan aide Mike Deaver and Robert Strauss, former head of the Democratic National Committee. O'Neill's daughter, Susan O'Neill, said she wants the evening's theme to be: "When Irish eyes are smiling, it will steal your heart away . . ." Settlement in DeLorean Divorce

The John DeLorean and Cristina Ferrare divorce battle ended yesterday with a split decision -- Ferrare won custody of the couple's children Zachary, 14, and Kathryn, 8, but the court upheld a prenuptial agreement preventing Ferrare from getting a large share of DeLorean's estimated $20 million fortune. In upholding the prenuptial agreement, Somerset County, N.J., Superior Court Judge Michael Imbriani accepted the decision of a California arbitrator who upheld the agreement.

In giving Ferrare custody of the children, Imbriani said, "The judgment is not between a good and a bad parent but between two parents." He said DeLorean traveled too much to be able to devote enough time to the children. He said their mother, who is now married to television executive Anthony Thomopoulos, could provide them with a more healthy family environment. End Notes

Former Treasury secretary Brock Adams has decided to run for the Senate seat now held by Washington Republican Slade Gorton. A group of Adams supporters are holding a fundraiser for him in a private Washington home tonight with a guest list that includes House Speaker Tip O'Neill, Sens. Edward M. Kennedy, Max S. Baucus, Alan Cranston and George J. Mitchell . . .

It's been what Rep. G. V. (Sonny) Montgomery considers a good year. He often boasts that his home state of Mississippi has the "best looking women," and this year he has escorted both Miss America Susan Akin and Mrs. America Donna Russell to White House meetings with President Reagan. He took Russell for her meeting Monday. Not only are they both from Mississippi, but both are from his congressional district. With a bit of hyperbole, Montgomery says his staff is checking to see what state Miss USA is from . . .

A fund-raising reception and auction for the victims of the Colombian volcanic eruption called "Washington Cares" will be held Dec. 18 at the residence of the Colombian ambassador. Among the honorary committee members expected to be at the fundraiser are Robert McNamara, Adm. Daniel J. Murphy, Harriet Pressler, Mary Jane Wick, Trudy Davis and Kathryn Iacocca . . .

Veteran actress Jessica Tandy collapsed Tuesday night during a performance of the play "Foxfire" at the Ahmanson Theater in Los Angeles. The 76-year-old star, recently seen in the hit summer movie "Cocoon," was able to speak minutes later and wanted to continue the play. Her husband, actor Hume Cronyn, 74, who was appearing with her, told the audience, "My wife is not feeling well." An understudy continued in the role. Tandy will remain in the hospital for rest and observation until the end of the week . . .

Blistex Inc., the lip-balm maker, has released its World's Most Beautiful Lips of 1985. Actor Don Johnson was voted "most arresting lips" and rock star Bruce Springsteen the "boss-est" lips . . .

Jazz musician Wynton Marsalis, a man with a mean horn, is putting aside his trumpet tomorrow to sing Christmas carols with a grade-school choir. Marsalis, who is appearing at Blues Alley and staying at the Vista Hotel, said he will sing with the Roosevelt School choir, accompanied by his pianist Marcus Roberts, in the Vista's lobby this afternoon.