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I second South Haven, MI. (www.southhavenmi.com) Just north of South Haven are some other beach towns with gorgeous, sandy beaches: Saugatuck & Douglas, MI. (www.saugatuck.com) Besides the beaches in all the towns, there are local u-pick fruit farms (blueberries, apples, peaches, plums, blackberries, etc.) which my kids love. There are also lots of cute shops and fun restaurants in the towns as well.
You might also look into Warren Dunes, MI (www.dnr.state.mi.us/parksandtrails/ParksandTrailsInfo.asp...) for camping and hiking and the Indiana Dunes National Lakeshore (www.nps.gov/indu/) for the same.
Enjoy!
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