Amid the cheers of 100 children at a camp in Prince William County yesterday, Nancy Reagan alighted from her limousine, tossed a volleyball, hugged a couple of campers, got paint on her hands in the arts and crafts shack and munched a campfire hot dog.

It was the second summer that Mrs. Reagan visited a Family and Child Services Camp for underprivileged children from the Washington area. This time, she brought along an educational puppet troupe to help dramatize to the 11- and 12-year-old campers the evils of drug abuse.

"As you see more and more kids involved with drugs at younger and younger ages, it really bothers you," said Mrs. Reagan, who has been campaigning nationally against the use of illegal drugs by the country's youth.

Mrs. Reagan's 2 1/2-hour visit began at 11 a.m., when she arrived on the volleyball field at Camp Goodwill, one of three summer camps in Prince William Forest Park supported by the United Way and by the Washington Post's "Send A Kid to Camp" program.

Last year, Mrs. Reagan visited another of the camps, Camp Pleasant. She was invited after she and the president made a $100 donation to the "Send A Kid To Camp" campaign. Yesterday, she wore the Camp Pleasant staff T-shirt she had been presented with last year.

After the volleyball game, Mrs. Reagan was treated to a demonstration of silk screening and then sat on the floor with the campers in a rustic cafeteria to watch the puppet troupe, "Kids On The Block," tell the story of Eric, a reformed drug addict and his drug-addicted friends, Joanne and Paul.

Afterward, the first lady climbed a path to a campfire site, where campers were roasting wienies on sticks. Campers Chanitta Perry, 11, and Nakeshia Lewis, 12, both from Washington, and Christine O'Neal from Prince George's County were all agog over the first lady's visit.

"My heart jumped when she first walked in, I tell you," Perry said. "But she really is a real person. Look at her. She's drinking bug juice and eating a hot dog. Do you think she eats hot dogs at home?"

"Probably not," said Lewis, who also said she thought Mrs. Reagan was very pretty.

"Where's Ronald?" O'Neal asked.

"He's back in Washington taking care of the country," Perry answered. "Oh," O'Neal said.