ENGAGED: "Sex and the City" costar Kyle MacLachlan, 42, and his longtime girlfriend, fashion publicist Desiree Gruber (whose clients include Naomi Campbell), plan to be married next April 20 in Gruber's hometown of Miami, says her publicist. The two have been dating for more than two years, since meeting at a chiropractor's office . . . SCHEDULED: After his new music CD, "Private Radio," arrives in stores on Sept. 25, Billy Bob Thornton, 46, will open Oct. 9 at the Warner Theater in Washington, D.C. His concert tour will also include stops in Chicago, New York City, Austin and L.A., reports USA Today . . . UNITED: Muhammad Ali, Michael Douglas, Antonio Banderas and Melanie Griffith are among those who have signed a pledge called Say Yes for Children, part of a global campaign led by a team of children's organizations. The campaign, say organizers, has gathered more than 3.2 million pledges worldwide since April, including those of scores of celebrities, Heads of State, and other leading citizens. The pledges are due to be presented to national leaders gathering in New York in September for a first-ever global summit on children. The Say Yes pledge form can be found online at www.unicefusa.org . . . HOSPITALIZED: Arizona Sen. John McCain (R), who turned 65 on Wednesday, successfully underwent a 70-minute surgical operation that day to treat a benign enlargement of his prostate, his office has announced. He is expected to remain hospitalized for one to two days . . . DIED: Gerard Zinser, 82, the last surviving crewman from the sinking of John F. Kennedy's PT 109 in the South Pacific during World War II, died in a hospital near his Florida home after suffering with Alzheimer's disease . . . INVESTIGATED: Basketball bad boy Dennis Rodman, 40, may have been involved in an incident Sunday in Newport Beach, Calif. (where he lives), reports the Associated Press. Witnesses reportedly told police that he allegedly sprayed a restaurant full of people -- at a local Hooters -- with a fire extinguisher after someone may have said something he didn't like. No arrest has been made, and Rodman's spokesman said he believed the alleged incident was a "misunderstanding."