The Idaho Falls Temple is one of the most famous LDS (Mormon) churches in the western United States and its evocative spire topped with a golden statue makes it one of the more recognizable landmarks on the Idaho Falls, Idaho skyline. The church lies along the famous Idaho Falls Greenbelt, a 6-mile stretch of trail through green, wooden parkland along the Snake River and the famous Idaho Falls waterfall. If you have a free morning during your visit to Idaho Falls, I'd suggest taking a morning to explore the Greenbelt and check out the scenic falls and the stunning white Temple along the way.
Aside from just the visual beauty of the temple and its surroundings, there Idaho Falls Temple also has a Visitors Center with some pretty interesting exhibits. The exhibits feature cased displays, charts, videos, and murals which are designed to help non-Mormons understand the Church of Latter Day Saints, its history, and its belief system. It actually makes for an interesting visit and the displays are appropriate for all ages. Again, I'd suggest spending a morning exploring the Idaho Falls Greenbelt before taking a brief tour of the temple and enjoying the nearby waterfall.
The Museum of Idaho in Idaho Falls is one of the most interesting museums around. it is undeniably a small-town museum with a modest collection and pleasant permanent exhibit, but what makes it so interesting is that it regularly draws world-class traveling exhibits like King Tut's treasures, European masters, and the famous Dead Sea Scrolls. Most of these exhibits only pass through big-city museums in New York, Washington, and San Francisco and it's such a feat that the Museum of Idaho has managed to bring them all to its exhibition galleries.
The museum's permanent collection is mainly based around the history of the state of Idaho and features some rather interesting and kid-friendly exhibits on the Lewis and Clark expedition and the founding of Idaho Falls. They even have a full-scale mock-up of an early Idaho frontier town that you can walk through and explore. The Children's Discovery Room is an especially nice addition and let's get learn about nature, animals, and history through fun little interactive displays.
As I said, the permanent collection is modest but you should have a look online to see what the temporary exhibit is during your visit. Who knows...you might be in town to catch one of the most famous exhibits on Earth! At $8 for adults and $6 for kids over 4, the admission prices are more than reasonable.