I lived in Northern MN for 25 years. Unless you have a decent boat you are pulling with you, I would pass on Voyageurs NP. It is almost solely water-based and there aren't any top notch RV campgrounds in the immediate vicinity.
Instead, travel to the north shore of Lake Superior, which is chock-a-block with 8 beautiful state parks, lots of great waterfalls, Superior National Forest, Grand Portage Natl. Monument (so you can still visit an NPS area!) Lots of state park, USFS and private campgrounds but best to get a reservation early. Burlington Bay CG (Two Harbors, Mn) and Grand Marais CG are town operated rv campgrounds right on lLake Superior.
