it is like a 2 hr drive from chicago north suburb, so it meets ur criteria (w/in 3 hrs of driving). I never actually been there before, but base on the reviews from tripadvisor,it seems like a nice place to go for a wkend getaway.
http://www.tripadvisor.com/Attraction_Review-g37006-d259610-Reviews-Indiana_Dunes_National_Lakeshore-Chesterton_Indiana.html
