You could spend a week or more just at the Quad Cities. Scott County Park is north of Davenport, IA on Hwy 61. Fabulous place - several CGs within the park, a swimming pool, old timey town (great ice cream there). Go to http://www.qconline.com and check the events calendar for all to see and do during your time. Suggest:
Niabi Zoo
Quad City River Bandits (AAA baseball). The outer field is actually built INTO the Mississippi River!
Ride the ChannelCat (water taxi between the 4 cities on the Mississippi)
John Deere Pavilion
and then lunch and ice cream at Lagomarcino's
Putnam Museum
Bettendorf has a great children's museum (The Family Museum)
I-80 Truck Stop in Walcott (largest truck stop in the world)
and then the Antique Truck Museum next door
On the Illinois side visit the Rock Island arsenal (must be US Citizen with valid ID or call in advance for foreign admittance)
Gas is cheaper on the Iowa side!
And in September you'll be too late for the deeelicious corn, but farmers markets will still have those luscious tomatoes.
Ditto on Amana Colonies (they are NOT Amish and do enjoy their German beer fest which by the way is also in September some time).
Good luck and have fun in good old I O WAY!!
Kathy & Scott
2018 Ford F-150 XLT
2018 Forest River Wildwood 27rks