As you will understand, your options will depend on the time of year and the weather. And within those options you have to decide how much you want it to be a useful NAVEX rather than sightseeing, and how much of an aviation geek you and your passengers are.
If you can’t get over the mountains...
Moruya (as already suggested) or Merimbula is a wonderful coastal sightseeing jolly. Or instead turn left at the blue and go to Old Bar or Luskintyre or Taree. Some useful procedural practice getting through military Romeos, but not so challenging from a navigational perspective.
But if you’re an aviation geek, maybe Wollongong and HARS is far enough?
If you can get over the mountains...
Temora (as already suggested, with muchos aviation geek value) or Cootamundra (short walk to town) or Cowra (usually friendly local flyers at the aerodrome) or Narromine (ditto with the local friendlies as well as a good museum).