Vented seats was available in all WK2 years, standard on the overland. Perhaps optional on some others but included in the Limited luxury group. You can check the features/options list on wk2jeeps.com to determine which models and trim vented seats were available. I think you either needed the overland or the limited with the luxury group II, however.
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac