Crossing at Niagara Falls and then taking I-90 is the long way around Lake Erie; taking 401/402 to Port Huron, and I-69 on the US side, is generally quicker. (Alternately one could cross at Detroit, of course. Going that way does make it easy to stop for a day or two at the Henry Ford museum and Greenfield Village, which are well worth seeing.)
I-90 to I-80 to I-29 is as good a route if you stay south of Lake Michigan as any. Avoiding driving through or all that near to Chicago is a good plan indeed. Another option is to take the ferry from Ludington, MI to Manitowoc, WI. The SS Badger ferry boat is of historical interest; however, the fees to cross are rather steep; you'd be looking at something in the vicinity of $400-$500 one way for two people, the motorhome, and the car.