About 300 of the 390 U.S. national parks are part of the Junior Ranger Program, which offers school-age kids the opportunity to learn about the park by filling out a short workbook or participating in an activity such as taking a hike with a park ranger. After completing the program, kids get a badge (or a pin or patch, depending on the park). For availability, check with the ranger station or visitor center when you arrive; some parks also put their Junior Ranger booklets online.
In addition to the Junior Ranger Program, kids can find a variety of activities designed just for them. Some parks, such as Sequoia, loan "Discovery Packs," backpacks filled with kid-friendly tools like magnifying glasses. Call ahead for availability.
Many parks also have general-interest programs that kids love. For example, Rocky Mountain National Park offers "Skins and Skulls," where visitors can touch a bear's fur and a marmot's skull, among other things, says Kyle Patterson, Public Information Officer for the park. "It helps kids—and adults—understand and explore in a hands-on, yet totally safe, way."
When you're through with the organized activities and are ready to head off on your own, remember that kids often take a shorter view of things than adults do, meaning they may need to be reminded once in awhile of why you're there and what lies ahead. A parent in Oregon recounts, "When I was hiking with my kids in Yosemite and they started to get whiny, I'd tell then, 'Hey guys, think of how much fun we're going to have at this swimming hole!' We'd also play games like I Spy." Other kids might like a scavenger hunt.