A block of rooms has been reserved at the Cobblestone Inn in Winterset. Let them know you're staying for the Drew/Lupkes wedding when booking for a discounted rate.
Just a stone's throw from the Jackson Building are plenty of modern campsites (electric and water hookups) for tents and campers. More information can be found here: https://madisoncountyfair.net/non-fair-camping.php
The Des Moines airport is closest, about 40 minutes from Winterset. Other airports in the broader area include Omaha (2 hours), Kansas City (3 hours), Minneapolis (3.5 hours) and Chicago (6 hours). There is very limited public transportation between cities.