Stop in Rochester, MN for the best ice cream (or sorbet) at Flapdoodle's. Heading east on I-90, take the Hwy 52 exit north into Rochester and Flapdoodles will be at the 37th Street exit. If you are looking for meals, things for kids to blow off steam, or anything else in Rochester, let me know.
We have family in Madison, so we are on I-90 often. There are lots of fun things to do just off of 90 in Wisconsin Dells.