Geli,
I'd suggest, along with Will,
Scooter's which serves Wisconsin style custard, which is slightly different than DQ style soft serve though darned if I know exactly how. Either way, Scooter's is a nice, clean, friendly place that you would enjoy.
Scooter's styled their custard after
Kopp's a, justifiably, popular custard stand in Milwaukee. The main difference, which is not insubstantial, Scooter's is 10% butter fat, Kopp's 14%. I prefer Kopp's, my doctor Scooter's.

Actually, unless you compared them side by side the difference would not be noticeable to most.
There is Dairy Star in the 3400 block of Devon, which puts it just over the Chicago border into Lincolnwood. I'm guessing at one point Dairy Star was Dairy Queen, looks exactly like Dairy Queen, and serves soft serve ice cream.
Enjoy,
Gary
Scooter's
1658 W Belmont Avenue
Chicago, IL 60657
773-244-6415
http://www.scootersfrozencustard.com/
Kopp's
Dairy Star of Lincolnwood
(847) 679-3472
3472 W Devon Ave
Lincolnwood, IL 60712