This is the closest airport to Delafield at about 30 minutes away. There is also a smaller airport in Madison, WI. It might even be beneficial to look at flights to Chicago and then take a taxi/Uber, bus, or train from there.
To book with the reserved room block, call 1-866-527-1498 and say you're with the Kuhn/Northrip wedding; the confirmation number is 10041325. Please make reservations before March 21st in order to take advantage of the discounted group rate.
For those staying at the Holiday Inn or La Quinta in Delafield, there will be a shuttle from Rustic Manor running from 3-3:50 pm to take you to the wedding venue. At the end of the night, the shuttle will be available to take you back to your hotel between 11:15pm-12:15am.