Advice on Timing of big trip - 2nd or 3rd term.

Hey folks, before I begin let me just say how much help it is reading all these blogs, treks and friendly banter between this community.

My wife and I are picking up the 4 kids out of school next year and heading off from Melbourne for the Western "half loop"of this great land of ours. Probably clockwise through to Perth, Kimberly, Darwin and back down through the centre. We have 15 -16 weeks with long service and annual leave. Would love to do the whole circle but would just be rushing way too much.

I'm just really struggling to work out whether to go 2nd or Third term. I'd love to see some thoughts from you all who have been there and done that.

Advantages of 2nd Term (April - June/July): A weeks worth of public holidays sprinkled through which means an extra week on the road, more importantly less croded (??). Main drawback or risk though would be that there will be more water around and thus perhaps areas not accessible (Would plan onm being up in Kimberly region in Mid May.) Whale sharks best in April which is a highlight on my kids "to do"" list.

Advantages of 3rd Term (July - Sep/Oct): More accessible especially up in the GRR region of kimberly, weather perhaps more friendly and less risk of a late wet season. But CROWDS are my big fear. I do not want to have to feel pressured moving from place to place in search of the elusive serenity and space.

I may be worrying over nothing. Any thoughts ??

Kids: 13, 11, 9 and 4.
Rig: 17ft bunk version of the expanda.
Wife: Gorgeous mother of the year.