X2 on the visit to Itasca state park. Well worth the drive.
Leech Lake and Lake Winnie are VERY large lakes and are good walleye lakes, so bring or rent a boat and your fishing poles. Bemidji is another town close by and worth a trip. Nice state park there too.
There isn't much on highway 2 between Duluth and Lake Winnie, with the exception of Grand Rapids, which is a lovely town and the birthplace of Judy Garland. If you have time, visit the Judy Garland museum. Lots of Wizard of Oz memorabilia, plus other items from her career. But the ruby slippers got stolen several years ago, and that caper has yet to be solved!