Lynn,
I would go one of the following two places, if you haven't already experienced them:
1) Iola (68C). Lunch is every friday at Noon, year round, rain or shine. You will see some of the most amazing, cool aircraft there - Lots of vintage stuff, often an experimental gyrocopter, several Ercoupes, a bunch of Cubs and Cub knockoffs... It's a little slice of aviation heaven. As others have said, stop at Clintonville (KCLI) afterwards for the cheapest fuel around, or if you just want something nearby, Waupaca (KPCZ) is about 10nm south of 68C.
2) Sheboygan (KSBM). One of the best on-airport restaurants anywhere. It's not well marked, but it's in the big gray building down near the approach end of runway 3. The fuel's not known for being cheap, but it is available, and the FBO will come down and fuel your plane at the restaurant.
Heck, you could do both - Get lunch at 68C on your way up on Friday, and then eat at KSBM on the way home.
I've been to all the other ones people have suggested so far, and while they're OK, they simply don't compare to these two.