At her nursery school graduation last week, Carolyn Mott, 5, told the audience she wanted to be an astronaut, an actress or president of the United States when she grew up. But Saturday, the little girl from Silver Spring changed her mind.

"When I get big," she said, "I'm going to be a cowgirl and catch animals like the Secretary for the Commercials."

She pointed to Secretary of Commerce Malcolm Baldrige demonstrating his rodeo techniques at the third annual Capital Children's Museum Membership Drive. For several hours, Jill Gore and Joseph Rosenbaum's McLean estate became a western ranch with cowboys and Indians, square-dancing, rodeo roping tricks and pony rides.

About 200 people attended the western roundup, including Baldrige's wife Margaret, Nancy Thurmond and former secretary of Labor Ray Marshall and his wife Patricia.

Thurmond, a member of the museum's board, appeared especially enthusiastic about the turnout. "The museum is a wonderful place for the children," she said. "This was a great way to generate interest."

A $30 membership fee entitles a family to one year's free admission. Charlene Reed, one of the parents who pledged to support the museum for another year, finds it "an educational experience for adults as well as the children."

Many of the adults also enjoyed the afternoon's activities. One woman, dressed in cowboy boots and hat, clapped wildly to the music. "I'm from cowboy country," she said. "This makes me feel like I'm home." She grabbed a man from the crowd and twirled him around. "Get with it, honey," she screamed, "this is the Wild, Wild West."

A group of children stomped their feet, chanting what they called "Indian war cries." The self-proclaimed Indian chief, 6-year-old Patrick Sullivan from Chevy Chase, had his face painted. "It's fun being an Indian," he said. "Being a regular kid gets boring."

Others tied their balloon strings together and tried to imitate 13-year-old Kevin Staples. He and his pony Champ delighted the children with a variety of roping tricks. His most fascinating routine was the dangerous "Texas Skip," a trick Will Rodgers made famous. The young cowboy spun the rope in a circular motion and jumped in and out of the center.

Baldrige, a member of the Rodeo Cowboys Association, said few people can perform the Texas Skip, adding that Staples "has a great deal of natural talent."

Baldrige and Staples then taught several of the children rodeo-style roping. Eight-year-old Tony Johnson wanted to try it, but he was "too scared and nervous" to approach the secretary of commerce. "He's important. He knows Nancy Reagan," he said with a shy, toothless smile. "I even think he knows the president.

After watching the demonstration, Carolyn Mott decided she should be an astronaut after all."My mom will never buy me a horse," she sighed. "I can't even have a dog."