Chicago’s Children’s Museum wants to relocate to Grant Park. “While it’s easy to get lost in such to-and-fro, the issue, in the end, is all about balancing precedent and progress: To allow one more museum to enter the park (the Art Institute of Chicago was granted an exception before its construction began in 1891) means that others invariably will follow. The risk is that more museums will clutter the park’s magnificent clarity, chipping away at Ward’s vision of serene open space. Is that where we want to go in the midst of a major buildup of residential high-rises around the park — even more buildings around its edges?”