I guess when he turns around 5 and starts going to school. He may quickly apply what he learned in school in a more visual way by going to the Mind Museum. It is actually the objective of the museum, to provide real objects or visuals to support the learning of an individual. :)
Their site says that "as long as they are old enough to walk and talk, [they] would find something worth their experience." I'd wait until my daughter is around 3 years old or just about preschool age though :)