It looks like you have a choice of routes, west to the "soo" or south to Niagara Falls. Either way, I always go on-line and order travel planners from the states I will be traveling through and see what they have to share. I find them quite useful as they contain localized maps and listings of campgrounds.
What interests do you have? How much time are you planning on? There is so much to see and do its hard to reccomend without having an idea of what to suggest. If you go thru Michigan you have the Soo Locks, Mackinac City, Frankenmuth, The Henry Ford in Dearborn. Go thru Niagara and you can hit Pensylvania Amish country, Hersey, or follow Lake Erie over to Cleveland to the Rock and Roll Hall of Fame. Dayton Ohio has the Airforce Museum which is worth the stop.
As far as the Smoky's go and Gatlinburg and Pigeon Forge its endless. If you like to hike then there are MILES of trails to trek. The National park itself is beautiful but really does not hold all that much to do. Clingmans Dome is the highest point in the park and worth a hike to get to. Newfound Gap is at the top of the road (rt. 441) that goes from Gatlinburg to Cherokee and lies on the border of TN and NC and has a large parking area to get out and take in the views.
The traffic in the Forge and G'burg can be VERY heavy so patience is in order but don't let that scare you away. Campgrounds are plentiful in the whole area. Dinner shows like Dixie Stampede are fun and they have good food too. Research the area to see if you find anything in your interests.
The Biltmore Estate is worth the price to see and it can take up the whole day. Go to their web site to get your tickets cheaper than at their visitor center. I would say to stay in the Maggie Valley area and do a day trip to the Biltmore. Wheels through time museum is in Maggie Valley and if you like motorcycles and old cars its worth a look too.
