I was accepted to my "reach" schools (Pitzer, Bard, and another one I can't remember because it was 7 years ago...) and wound up attending my 2nd safety, which was also 2nd to last on my list of colleges in order of preference.
That 2nd safety was UC Santa Barbara, a huge public university that initially seemed totally overwhelming and "not me" (I came from a very small high school with a graduating class of 29 and lots of individual attention). I ended up there because the financial aid from the private schools was either nonexistent or inadequate, and the affordable schools I had to choose from were all large public universities (UC Santa Cruz and Oregon were on the list too) that I'd had as safeties.
What made the biggest difference for me was visiting the campus. I was determined to find SOME way to pay for private school, but I spent a week in Santa Barbara and a full day on campus with a tour, etc. and that sealed the deal. I'd really encourage your son to visit both Kzoo and Michigan and spend some time on campus, really trying to imagine himself there--it may completely change his mind.
I'll note that UCSB was not all roses, and though it didn't fulfill all of my hopes/expectations for a college, I made it work and created a wonderful experience for myself. Greek life helped a lot
I'll be crossing my fingers for you guys for an acceptance and great aid package from Brown!