I second many things said here. Beware that the North shore can get cold even when rest of Minnesota is warm, dress for all kinds of weather. Agate picking is fun and popular. All state parks are a treasure, we’ve done them all, but tettegouche is best. Temperance River* is second best, great hikes near highway. Underrated and away from weekend crowds: Crosby manitou, though bugs can get bad depending on what time of year. Bean and bear hike is one of the best hikes in the Midwest.
*Edited for temperance river (not cascade), though cascade is nice too