Ranger Adventure Hikes, offered by the park rangers at Yellowstone, are a great way to engage the kids and get beyond the boardwalk. One hike takes intrepid walkers through cool aspen groves and sunny meadows to tranquil beaver ponds that a promise of wildlife sightings. Another hike takes trekkers to backcountry thermal areas. Family Travel Tips: Ranger Adventure Hikes are offered each summer from mid-June to late September. While none of the hikes are specifically geared to families, kids are welcome on all excursions. Hikes are free of charge. Not all hikes are graded easy. The shortest hike is 4 hours long. All hikes are limited to 15 participants. Advance reservations are required and must be made in person at a park visitor center. Be sure to wear proper footwear and carry sufficient water, park rangers have turned away ill-equipped participants on more than one occasion.