ideas for traversing the Northern tier states

[Cammy]

My wife and I are planning our annual trip East from Sacramento CA area to Mid-Michigan. We have done the I-80, I-70 and I-40 routes and this year would like to cover the Northern Tier states. On the return leg we would leave central Michigan exit the state through the UP and enter Wisconsin. From there we plan to cross into Minnesota, hit North and South Dakota, Montana, Idaho Wash, Oregon into Ca. I-90 should cover Montana and points West. Need ideas for efficiently tackling the Dakotas. it looks like I-94 to Fargo and then I-29 South to I-90 would do it but wondering is there a more direct method.