There are lots of things to do in the area. The Hagerman Fossil Beds National Monument is very cool. It's an ice age site that contains the fossils of sabertooth cats, mastadons, cave bears, horses, etc. My little girl loves the place.
Shoshone Falls are also very cool. The Snake River Gorge is always amazing, too.
If you're up for a bit of a drive (20 miles or so), there's an ice cave a few miles north of Shoshone. Sun Valley and the Sawtooths are within easy driving distance, too.