Northern MN up North of Grand Rapids, along hwy 38 that is a beautiful drive from Grand Rapids To Effie, the road goes through Chippewa national Forest. Once you get to Effie there are not a lot of people.
The Bigfork Valley is beautiful, the river is one of the few left unspoiled great fishing out of a canoe,
Another nice drive is the North Shore from Duluth to Grand Maris and North to Cananda, You then can take Hwy across Cananda to International Falls and come back to MN, the trip across Cananda is the North side of the Boundry Waters and has some great Falls.
If you want to spend all your money in one day just go to the Mall of America and let your wife loose.
There are lots of small Campgrounds in MN that are not part of the State system county campgrounds and such.
If you would like a rodeo the North Star Stampede in Effie MN has been around for over 40 years and is quite a spectical for a town of 100 or so and you can take a picture of the big mosquito in Effie
There is also the Spam Museum in Sotheren MN that is also good.
Hope this gives you a idea or two