We recently finished a cross-country trip from PA to Seattle and included several national and state parks (Grand Canyon, Sequoia, Redwoods ,and a few others). My daughtes are 4 and 7. We kept the hikes short and definitly included the Jr. Ranger programs. Both girls used a Mountainsmith backpack, which was plenty big to carry their stuff (some toys from home helped them feel less out of place). We kept the hikes short and let them help select some of the places to see and explore. My mother bought them a poloroid camera for instant photos which they loved (and make good scrap book fodder). Both got new hiking shoes that let them scrable rockes and splash in streams; the off-trail stuff was a big hit.  We found little paper bags that included a forest scavenger hunt list on the side (Target, I think). The girls also like painting small rocks to decorate our campsite and leave for the next kids (our town had a similar "hidden art" program). Basically, we kept a bunch of small activities in mind to break up the long activities (hiking, setting up/tearing down camp) as well as let them explore on their own a bit and help decide what to do. Both did really well for the length of the trip.  ... View more