A few ides for your consideration.
Up in Green Bay...
Lambeau Field and the Packer Hall of Fame
Green Bay Botanical Gardens
National Railroad Museum
New Zoo and Adventure Park
The Automobile Gallery
The Neville Museum
Bay Beach Wildlife Sanctuary
In Appleton....
The Butterfly Garden of Wisconsin
History Museum at the Castle
Bubolz Nature Preserve
In Oshkosh...
The Paine Art Center and Gardens
Menominee Zoo