Lilly B. Reeves, a 20-year resident of Anacostia, turned 103 on July 18, and about 200 friends and family members will help her celebrate Sunday at Isle of Patmos Baptist Church in Northeast Washington.

A native of Lancaster, S.C., she taught school there for one month and then married the principal. She is the mother of 13 children, the grandmother of 54, the great-grandmother of 27 and the great-great-grandmother of 10. Her husband, Charlie, died in 1950.

Her 10th child and namesake, Lilian Walker, 65, also lives in the District.

Now living at a senior citizen facility, Reeves attributes her longevity to "good living . . . and prayer." She continues to be self-sufficient, with plenty of time for family and friends. "I'm having the time of my life right now," she said. "I have no problems, and I am enjoying myself." Foundation Names Leaders

Two District men have been named to leadership positions at the regional chapter of the National Kidney Foundation.

Ben Cotten, a local lawyer, is the new chairman of the board, and George W. Jones, a urologist, is the chairman-elect.

Cotten, a partner in the D.C. law firm Cotten, Day & Selfon, has been a volunteer at the foundation since 1983. He served three years on its executive committee and two years on its public policy committee.

Jones has been active with the National Kidney Foundation for many years and its board vice chairman since 1987. He also helped launch a urologic screening program in D.C. public schools. Nursing Manager Honored

Monica Koshuta, administrator of Hospice of Washington, was recently named the top nursing manager in the area by the District of Columbia Nursing Association.

Koshuta, a registered nurse, has headed the hospice program for four years after serving as its clinical director for two years. She is also president of the advisory Hospice Council of Metropolitan Washington Inc.

"We are really pioneers. We're venturing into new areas for the care of the terminally ill," she said. "The challenge is to meet the culturally diverse needs of this community, and to provide quality care to all those in need."

From 1958 to 1970, Koshuta served as a consultant to health officers at U.S. embassies in Cyprus, Italy and Brazil. In recent years, she has been active in the AIDS Demonstration Program of the D.C. Commission of Public Health and has been a member of the advisory committee of the mayor's task force for the development of licensing regulations for hospice care in the District. With her master's degree in nursing from George Mason University, she also has been a clinical instructor at the University of Virginia campus in Falls Church. Down the Yellow Brick Road

Dianne Boggs, of Cleveland Park, got together 80 neighborhood youngsters and spun her usual theater magic again this year, mounting a series of four sellout performances of "The Wizard of Oz" at Sidwell Friends School last weekend.

The performances by the Summer Musical Theater Workshop, now in its eighth season, featured a cast of young people and a technical crew of local teenagers. In all, nearly 1,700 people attended the productions, which followed six weeks of rehearsals.

And, yes, that was Sarah Wolfson playing Dorothy, John Leonard as the scarecrow, Patrick Tansor as the tinman and Michael Sachse as the lion during the weekend's matinee performances, aimed especially at families with preschoolers.

The four other performances starred young thespians Kate Earls as Dorothy, Nell Mooney as the scarecrow, Damon Metz as the tinman and Cecily Macrory as the lion.