We know flights are very expensive but can offer a little advice.  Please monitor the RSS feed at the bottom of our site for Hawaii travel deals including airfare sales.  If you have credit card miles and can find flights for 40,000 miles or less, this is usually one of the best redemption values from the midwest.  I would try to book as early as possible but keep in mind the following advice from Best of Hawaii for when the best time to book is (it is a bit of a gamble to wait as you just never know).

Another bit of advice.  Select window seats on the left side (‘A’ seats) of the aircraft for great views of the island before landing on Kauai!