Grand Haven State Park has a great beach and it's very popular on summer weekends. Crowds of visitors stroll the wide walkway along the Grand River between the state park and the downtown restaurants and shops. The beach itself is wide and long with plenty of nets for beach volleyball, an ice cream stand, changing rooms, and lots of smooth sand. The park is right at the edge of town so it doesn't have the wooded dunes that some other Lake Michigan parks offer. It doesn't really have any grass-- just one big beach.
The state park campground has a great location but it's basically a parking lot on the beach. The RVs are packed tightly, with just a line painted on asphalt to separate campsites. I wouldn't want to camp there with my tent.
Grand Haven is a little over an hour from Kalamazoo.
I teach economics at Kalamazoo College. My wife is also an economist. We were on sabbatical in Europe for the 2014-15 academic year. (Salamanca, Spain, followed by Oxford, UK.) We were in Uruguay for the 2006-7 academic year.