Fort William is great and you should allow 3-4 hours - they have a huge parking lot so should not be a problem - I would call them first. Did not know they had a campground full hookups for $35 is good
The falls as I remember has a small lot - not sure on the time depends on how many trails you would take
You will pass some great Minnesota campground on the way up in Grand Marais and Two Harbors plus this falls that is literally at the US - Canada border
2012 Winnebago Journey 36M Cummins 360
2014 Jeep Cherokee
492 Campgrounds,107K miles driven in our Winnebago motor homes and 2360 nights camping since we retired in July 2009, 41 National Parks