Love is in the air this Valentine's Day. Tennis greats Andre Agassi, 29, and Steffi Graf, 30, have apparently decided to seal their love match and wed, says a German newspaper. The setting will probably be Las Vegas (Agassi's hometown) on June 14, Graf's birthday and the one-year anniversary of when their romance first ignited, five months after Agassi's divorce from Brooke Shields . . . Actors Christian Slater, 30, and Ryan Haddon, 28, got hitched (both for the first time) Saturday night at the Beverly Hills Four Seasons Hotel. The Slaters have a son, Jaden Christopher, who was born last April and is with his parents on their Hawaiian honeymoon . . . Speaking of offspring, rock star David Bowie, 53, and his wife since 1992, Somali fashion model Iman, 44, announced on Sunday that they are expecting their first child, in August. Bowie has a grown son, Joey (formerly known as Zoey) from a previous marriage, while Iman's daughter, Zulekha, is from her marriage to pro hoop star Spencer Haywood . . . Meanwhile, an uncoupling: singer Diana Ross, 55, and her husband of 14 years, businessman Arne Naess, 61, officialized their divorce Friday in the Dominican Republic. They had married in 1986 and have two children together, as well as others from previous relationships.