Boot Hill Museum, Dodge City. The live gun fight recreation is fun, sure, but the museum itself is awesome.
St Jacob's Well, south of Minneola. I haven't been there, but my good friends like it. If you just want to get out, stretch your legs on a short hike, and see some nature, maybe it's worth it.
Fick Fossil & History Museum, Oakley. I've only been there in 4th of 5th grade, but I remember liking it back then.