Hi, George;
Just a thought or two. While the uni (as you call it) has a good breakfast deal at an all-you-can-eat price, sometimes you don't need that much food. Another option at the dorms is The Terrace, which is a small area on the first floor of Gruenhagen; this is more ala carte of a continental breakfast scope.
Fruit, bagles, toast, pastries, cereal, coffee and juices are about all they have. But, if you just want a bagel w/cream cheese, a banana, and a cup o' Starbucks, you'll get out for around US$3.
I've never made the drive from Appleton, but if you're adventurous, you'll probably bump into someone in the terminal who's heading to Oshkosh and would give you a ride. It'd be a good bet that just about 98% of the folks on any given flight that day will be heading to the show.
There's normally a shuttle bus that runs from the grounds to Appleton, but I don't recall the day they start it. The planning section of the Airventure.org website lists Nationwide Travelers at 920-734-5620 who provides a shuttle service from the airport. They may be able to give you better information.