Now called Frontier Homestead State Park as of 2009, formerly Iron Mission State Park. 

Lots of pioneer information on how Cedar and area started in late 1800's. Very few hands-on stuff for young kids.  The first tuesday of every month is free.  There is Preschool story time - a short story about what pioneer kids did that time of year and an activity for the kids.  This might be most accurately described as a museum.