A lot of Chicago-area families have houses on various lakes within a couple of hours drive of Chicago. Wisconsin and Michigan are the obvious choices and Lake Geneva is the most obvious choice. However, I have stayed with friends at some wonderful homes on smaller lakes. The key is to find nice ones that are available for rental. (Most of the time the nicest ones are not rented but there are exceptions).

It's not hotel service but a beautiful lakeside home with a sandy beach and options for getting on the water (ask about renting boats) is a great vacation.