JD if I understand you correctly, you want to know when US schools start summer break because of its possible effect on flight loads.
Frankly I don't think you have to worry, US families usually plan their trips to Australia well in advance. The LAX/SYD loads are pretty well set two weeks out, what will give you fits are those last minute non-revs.
Disneyland Info - To get the most bang for your buck go for the mulit-day park hopper pass, good for Disneyland & California Adventure.