Thirteen-year-old Gregory Hooke rolled up to home plate at Falls Road Park and, with a little help, whacked the ball down the third base line. He smiled broadly as his twin brother, Matthew, pushed him safely to first, his wheelchair spinning up dirt along the way.

Being a teenager with a disability can be an isolating experience for a child and for his parents. But on Sunday, close to 200 Washington area families gathered at the park in Potomac to celebrate two decades of a program that they say has provided a community for young people with disabilities, a place where they can socialize and play sports at their own pace.

“He gets an activity that’s all his own, and he gets to be like any other kid,” said Patty Hooke of Chevy Chase, whose son Gregory has cerebral palsy. “It’s beautiful.”

What began at a Montgomery County elementary school in 1992 with fewer than a dozen families has grown to include more than 300 in the District, Maryland and Northern Virginia. Kids Enjoy Exercise Now, or KEEN Greater DC, matches young people who have a variety of disabilities with volunteers to swim, bowl, play basketball or tennis, or play soccer with a coach from D.C. United’s foundation.

In its 20 years, the program has linked thousands of volunteers — many of them students and young professionals — to children with Down syndrome, cerebral palsy or autism.

“You realize these are just kids,” said Tracey Wright of Silver Spring, who brought her 10-year-old son, who is autistic, to the event. “We have a generation of kids just with autism, and society is going to have to find a way to include and embrace them.”

Having a child with special needs, parents said Sunday, often means that going to something such as soccer practice is not as easy as just showing up. Their children don’t necessarily move at the same speed or in the same way, and they might not be able to follow directions or understand the dynamics of a team sport. Matching kids one-on-one with an adult, they said, gives them the freedom to define their own success. That can mean learning to hold a ball or just walking halfway across a basketball court and back.

“There are no rules; there is no competition,” said Beata Okulska, the group’s executive director. “It looks like chaos, but when you get involved, there’s a lot of sense to it.”

The program is free — a welcome break, parents say, from the usual routine of costly therapy sessions.

The program appears to have had as much of an impact on the children as it has had on some of the volunteers. Laura Partridge was a certified public accountant working 70 or 80 hours a week at a large firm when she volunteered one weekend in 1994. Partridge said she soon realized that she was looking forward to being with the kids all week and decided to go back to school to become a teacher.

“The workweek could have been horrible,” said Partridge, who now teaches middle school math in Alexandria. “But it was always uplifting and rewarding to see those kids smiling.”