Hazel Reddick lunched downtown recently with her 5-year-old son Saul. They ate at Child's Play, not a new restaurant, but downtown's first privately run day-care center.

The center is at 16th and K streets NW, in the midst of the K Street office corridor, and parents are permitted to visit their children during lunch and at other times during the day.

"I can pop out of work sometimes and take a 10-minute break," said Reddick, 37, an airplane ticket agent who works in the same building as the day-care center. "It's so close, and I wanted contact with him in the daytime. I take him out for pizza for lunch sometimes and he plays video games. He thinks it's great."

Open since January, Child's Play is in the basement of an office building. It has four classrooms, largely decorated with the children's art work, a large play area with blue skies and clouds painted on the ceiling and old-fashioned pane windows with bright yellow trim.

The center can accommodate about 120 children, ages 2 to 6, but it has an enrollment of 32 because construction delays forced the business to open after the traditional school year began in September, said founder Alexa Betts.

Betts' search for a downtown day-care center for her own toddler son six years ago -- and her finding that none existed -- launched her business career. She looked for space in the blocks bounded by 16th and 18th and M and H streets NW, and she conducted market studies that showed that parents working in that area had 36,000 preschool-age children. That was five years ago.

"People said you could never do day care downtown and make it affordable," Betts said. ". . . There have been lots of studies that say parents want their child care near the home, and . . . in rural or nonmetropolitan areas. That's probably true. They all ignore the needs of working parents in metropolitan areas."

Of the District's 259 licensed day-care centers, about a dozen are near downtown; most of those are in federal agencies. The federal departments of Housing and Urban Development; Education; Labor, and Health and Human Services have operated day-care centers since the early or mid-1970s and charge $45 to $65 a week. The Senate established a day-care center for its employes a year ago.

The World Bank, after 10 years of negotiations between top officials and employes, has agreed to open a facility for 90 children in 1986 near its headquarters at 18th and H streets NW to serve its nearly 6,000 employes.

More day-care centers may be coming to downtown. The YWCA plans to open a center for 65 children in July at its headquarters at 9th and F streets NW. The center, targeted to downtown workers, will cost about $75 a week and stay open until 8 p.m.

Murray Seeger, a spokesman for the AFL-CIO, said day-care facilities at work sites for employes' children are among the union's newest collective bargaining issues.

Recent studies show that nearly 60 percent of married mothers with children age 5 or younger are in the labor force, compared with 37 percent in 1970, he said.

"It's one of those benefits that's on the front tier," Seeger said. "Everyone thinks it's a great idea, but it's hard to negotiate."

The District government plans to put a day-care center in the city's new municipal center at 14th and U streets NW for the children of employes.

Child's Play offers wooden play equipment and toys, catered hot lunches and snacks, and daily jaunts to nearby Lafayette Square in good weather.

Parents cited convenience and crowded day-care centers in their neighborhoods as the major reasons for choosing Child's Play.

"Its location was one concern," said Janet Guthrie, a station relations associate at the Corporation for Public Broadcasting, while her son Steven, 3, ate lunch nearby. "We drive in every day, and that additional time together is important."

The center, which is open from 7:30 a.m. to 6:30 p.m., charges $100 a week per child. Law firm office manager Nancy Adams, who enrolled her daughter Abigail, 2, in Child's Play, said, "It didn't seem any more expensive than what I was paying, and it allows Abigail to have a shorter day."

Previously, Adams said, she left her daughter at the sitter's house in their neighborhood at 7 a.m. Now, the two start the drive to work at 7:15 a.m.

"It's higher than most other day-care centers, but it's probably a lot better than most . . . ," said Terry Moe, a political scientist at the Brookings Institution who commutes from upper Northwest daily with his 2-year-old daughter Caitlin.

Betts financed the $300,000 cost for her center with a Small Business Administration loan and backing from a group of local radiologists. She said it should make a profit in two years.

She said she hopes to open a second center at 22nd Street and Virginia Avenue NW near the State Department this fall; she has plans for others to follow in downtown Bethesda, Rosslyn and Tysons Corner.