Fate seemed to be against the annual fund-raiser for Africare, one of black Washington's most popular events. Andrew Young, U.S. ambassador to the United Nations and the scheduled speaker, was still recuperating from surgery. And the Iranian Embassy, the party's popular location for two years, was under new management and wasn't available.

Yet, despite those setbacks the Africare benefit attracted 500 people yesterday to hear Young's substitute, Donald McHenry, the second man at the U.N., Richard Moose, assistant secretary of State for Africa and Oscar Brown, the folk-soul entertainer-and to dance and dine last night in the Organization of American States monumental marble halls.

There were some slight grumblings about the change of location. "Not as much glamor when you don't have all those rooms and mirrors," said one guest. "More people buy a ticket for an embassy party," said William Steen, head of the Washington chapter of Africare, the humanitarian assistance and training group that sponsors the benefit. "Plus, the Iranians picked up the tab. We have to pay for this." Smiling, C. Payne Lucas, the executive director of the group said, "I don't have to justify the OAS"-the use of the building had been arranged through the Haitian Embassy as part of its goodwill effort to reopen relations with several African nations.

The Africare benefit is one in which the usual Washington blend of the serious and the social is blatantly separated. Most of the serious discussion took place before the OAS party at a late-afternoon gathering at the State Department. There all of the speakers discussed the recent change of leadership in Uganda and the elections last week in Rhodesia.

Reviewing the changes in American policy toward Africa in the last decade, McHenry, who was the chief American negotiator on the Namibia question, said, "It's not up to the United States to decide the leadership of poor countries-we have to emphasize the process." Moose characterized the next two weeks of American decision-making on Africa as "difficult days." The administration has to evaluate the Rhodesian elections, he said, and decide whether to lift sanctions against the Salisbury government.

"In Uganda we expect to normalize our relationship very soon. The first American teams will arrive in Uganda early this week, " said Moose. Bishop John T. Walker, chairman of the Africare board, announced that the group will be working in Uganda and added a personal note to the opinions of Idi Amin's ouster. "He was a tyrant who deserved to fall. I know of at least 200 people he killed," said Walker, who once taught in Uganda. "There were some misguided blacks who think he was attacked because he was black and African. I'm glad his end came." CAPTION: Picture 1, Donald McHenry, by Margaret Thomas; Picture 2, From left, Marion Barry, C. Payne Lucas, Golda Butcher, Bishop John T. Walker, by Fred Sweets-The Washington Post