Benjamin Richter, 6, looks at a hermit crab in an aquarium provided by the Marine Science Consortium during the third annual Active Kidz exhibition Fair Oaks Mall in Fairfax. (Evy Mages/For Capital Business)

A throng of kids surrounded the Mad Science booth at Fair Oaks Mall in Fairfax where a bespectacled man in a lab coat demonstrated how dry ice can make a quarter wiggle.

Mad Science was among about 50 exhibitors, nonprofits and community agencies trying to sign up young people for their spring and summer camps. The third annual fair connected about 2,000 families with youth-service providers offering theater, science, music, sports and other activities.

Hosting the event was Active Kidz, a company that organizes exhibitions. Karen O’Conner-Joyner, an accountant at the State Department Federal Credit Union, started the company four years ago.

O’Conner-Joyner said she doesn’t make much money on the events — only a little bit more than her expenses. She said her main aim is to encourage more kids to participate in health and wellness programs.

“I put these events together to promote kids being active with activities that they may not be used to,” she said.

Four years ago, O’Conner-Joyner established KOJAM Productions, the parent company of Active Kidz and a few other exhibition brands, after seeing how out of shape many young people were. Now her commutes home from work are mostly spent calling vendors and shopping mall staff to organize the five exhibitions she does each year.

A high-ranking baton twirler as a youth, O’Conner-Joyner said her experience volunteering as a dance coach at her son and daughter’s middle school prompted her to start the company. “In teaching dance, I was seeing how kids were out of shape and needing to be more active and how kids weren’t exposed to things to become active,” she said.

O’Conner-Joyner pays the venues between $2,000 and $10,000, and charges for-profit vendors between $200 and $700. Officials at nonprofits, who aren’t charged, say they are grateful for the exposure.

“They really help us out with this event,” said Kathleen Heck, manager of The Box, a local hockey league. “We’re a nonprofit, so we always need help with the money.” Heck said she got 20 sign ups during the exhibition.

“We do a lot of flyers and put ads in publications but it was nice to talk about our upcoming race face-to-face,” said Wendy Allen, chair of Strides for Success, a race organized by the Junior League of Northern Virginia, a women’s organization that promotes volunteerism.