I 35 North of Twin Cities

We did a similar trip many years ago with our young kids. Sounds like you have your reservations already, but it's nice to break things up on the way. We stayed at Jay Cooke state park our first couple nights and drove into Duluth to do the train, canal, etc. and then drove up to Gooseberry Falls state park and stayed there a couple of nights doing the things around that area and then ended up in Grand Marais for our last few nights. It was a relaxing way to see the entire north shore and allowed for some short hikes as well as visiting all of the stops on the way. Make sure to pick up the north shore guide which includes all of the mile markers for interesting stops along the way.