In Seattle’s Cal Anderson Park, about 1,000 men and women turned out for an adult recess one Saturday earlier this month that included kickball, hopscotch and tetherball, along with chicken nuggets and grilled cheese sandwiches.

“I thought back to the last time when I really had fun, and it was these games when I was a kid,” said Clay Lundquist, managing director of Center Stage Entertainment Marketing, which produced the recess…

One afternoon last week, a group of mostly retirees meeting in the library community room played games of jacks and Yahtzee with oversize foam dice. “Oh my gosh, there was so much laughter,” said Tonya Gardella, manager of the Akron-Summit County Public Library branch. “I honestly feel like you are using a different part of your brain—the part for having fun.”

The games do exact a physical toll. Greensboro’s Ms. Hance said she woke up surprisingly sore the morning after she crawled and jumped her way through an obstacle course made out of bounce houses. “You go in and think, ‘I can do this,’ but I’m not 12 anymore,” Ms. Hance said.