At this time of year up here (the run off) you can't miss a good old sight seeing tour of Kakadu and its beautiful waterfalls. They are not open to road traffic last I looked (2 weeks ago) but I hear a flight over them is spectacular. Nice paved airfield at Jabiru too with food, fuel etc. Have a super time and make sure you spend at least a night in beautiful Darwin - Thursdays are Mindil Beach Market nights (if you like doing the crowded tourist thing) or Saturday morning is Parap market day - gotta have a seafood laksa!
Cheers, NFR.