The drive from Chicago to OSH is pretty painless, and takes about 4 hours- you could easily make that trip and spend two days at OSH- and still not have enough time there. Skip Milwaukee.
But, there's no place to stay anywhere near OSH. Overnighting in Milwaukee just because there are rooms available -- but I would consider some place else south of OSH to overnight. I hear Milwaukee has some pretty rough neighborhoods, yes....?
