What to do in Missoula, MT in April with Kids

I am traveling to Missoula in a few weeks with my 6-year-old - I’m wondering if anyone has any suggestions/recommendations of things to do for kids his age while we are there? Either in Missoula or surrounding towns? April is a hard in-between seasons month to be up there…. bonus if you know of places or activities involving fossils/rocks/gems/natural history - thank you all!