How far to travel with only 2 weeks vacation time/year

I have a friend with a motor home who burned one tank of gas last year. And he's gone most of the Summer.

We're fortunate to have 4 state parks, a city campground, TVA campgrounds and private campgrounds within an hour. We don't really need to travel to camp with the Tennessee River running through town.

Given 2 week's vacation, surely there's somewhere you'd like to stay in Michigan--even if it was on the Upper Peninsula.