The Discovery Center of Idaho is an amazing place for kids (and adults!) of all ages. They have an extensive collection of hands-on science and technology exhibits. They also feature revolving themed exhibits that change every few months.
Be sure to check out their calendar as they host quite a few events throughout the year and many of them deal with STEM learning for kids.
If it’s raining outside this is a really great alternative activity location to take the family. If it’s not raining though, you can visit the Julia Davis Park for a walk or paddle boat ride or stop by the zoo. Both are near by to the Discovery Center. If you’re in the mood for another learning museum you could also visit the Idaho State Museum.