We recommend downloading All Trails to find a hike that is a good fit for you and your family. Be sure to rent bear spray and know how to use it. The park is known for having both grizzley's and black bears. Know the difference and what to do if you encounter one. Making noise helps deter bears from coming around. You will notice some people clap and say "hey bear bear! Hey bear!" in an area known for frequent bear sightings. I also recommend looking at the parks website for trail and road closure as well as bear activity and other important information.
Go visit the oldest and the country's very first national park! Yellowstone is a huge park and you could spend forever there. Lamar Valley is a good place to go to see wildlife. You will be tired of seeing bison by the time you leave. Old Faithful, the Weeping Wall, Grand Prismatic Spring, Grand Canyon of the West. All awesome places to go. Again, be sure to check out the parks website and be Bear Aware! Rent some bear spray!