What about Giordano's, Maggiano's or Pompei? I haven't been to Ditka's or Harry Caray's, but those are pretty expensive from what I gather like the Weber Grill on Butterfield. Maybe a trip to Uncle Bub's in Westmont on Cass Ave. (same street as Midwest Rd.) could be fun too if they want a local place. If you want to go to a more local Greek restaurant you could try Kappy's, Simon's (both in Villa Park on Roosevelt Rd.) or Omega (Highland in Lombard by Yorktown Mall). There's nothing magical about Oak Brook that you have to drop $100 on a steak dinner at a big name restaurant. Besides the Giordano's stuffed pizza, an Aurelio's thin crust pizza for carryout is always good too. There's one of those on Roosevelt Rd. near Kappy's and Outback. I also think Portillo's is a nice place for lunch on Butterfield or 83.
If you have time Oberweis Dairy is the best local chain for ice cream in my opinion. There is one on Butterfield and York in Elmhurst (northeast of Oak Brook) and on Odgen Ave. (south of Oak Brook) in Westmont.