There are plenty of activities in New Buffalo- there are public beaches on the lake, antique stores everywhere, a nearby casino, public golf courses, and dunes. You're also welcome to hang out at Sans Souci to chat and relax with other guests and family.
We're not organizing any outings in advance (because there are so many choices!) but there will be plenty of appealing options to suit everyone.
You can browse www.newbuffalo.com for ideas and maps.
Search for the Southwest region on http://www.michigan.org/ for even more suggestions.