One thing I want to particularly comment on was the series of signs in the line for the Log Jammer. Check out the "Log Jammer" set of pictures at http://www.explanatoids.com/allexplanatoids.asp# .
I'm digressing for a moment, and I promise that it'll be relevant: my father (a professor of chemistry) rants from time to time about children's science museums. He says he's watched kids at those museums, and they don't learn much science from the interactive exhibits; they just race from one exhibit to the next looking for buttons to push. And these exhibits just demonstrate funky science facts; they don't educate kids in the scientific method.
This Explanatoids set of signs is a strong contrast to that, because it really does teach about the scientific method. It poses a question ("What affects how wet you get on the Log Jammer?"), proposes three hypotheses, and then designs, carries out, and reports an experiment to test those hypotheses. This set of signs really demonstrates the process of scientific discovery (and on an interesting question, too).
(As a side note, a project like this would be well within the capabilities of a junior-high student, and stand a great chance of winning a science fair contest.)
Unfortunately, it appears from the Explanatoids website that most of the sign sets are of the form "here's some science facts relevant to the situation" instead of "here's an experiment by which we investigated some relevant science." Still, I'll give them some points for inserting science-as-facts into playgrounds and ballparks. I wish them well with their mission.