Since you mention hiking and water sports, I'm going to assume you're more interested in an "up north" vacation than exploring the Detroit area.
I highly recommend the Lake Michigan side of the state, around Ludington, Sleeping Bear, Traverse City areas. Fabulous beaches, wonderful state and national parks with a huge range of wildlife and scenery to explore, rivers with canoe/kayak liveries all over the place, and amazing fishing. There are also some lovely wineries with tasting rooms on the Leelenau Peninsula, if that's something that interests you.
Also, if you love hiking, the Upper Peninsula would probably be right up your alley. Beautiful, unspoiled forest as far as the eye can see. The shipwreck museum at Whitefish Point is really interesting, you can tour old copper mining sites at Houghton/Copper Harbour, and Isle Royale National Park is one of those places you have to see to appreciate.
Mackinac Island is fun but not a destination in itself, IMO. Great for a couple of days but not as the focus of a whole trip. But it is very easy to combine a couple days there with a few in the Traverse area or as an overnight stop on your way to the UP. Frankenmuth, on I75N is the same way - a nice place for an overnight or a short shopping-and-dinner stop to break up the drive, absolutely worth seeing (especially Bronners!) but not worth a trip to itself.