I would check prices on every site possible AND i would suggest using Disney Direct or Purchase hotel/tickets through Disney and then pay for flight seperate.
The first time we went we stayed at All Stars Movies it would be ideal for your son.
If you book ahead and keep an eye out for Free Dining then i would suggest POR OR POFQ. If you can get Free dining it is the best thing to use and i now wouldnt go without it.
I have been using the boards since 2004 and been to Disney World 4 times, I am not an expert but others have helped me alot and still do today.
As for Heat Dont Go June to August, We went in June and the children hated the heat. We have been end of September and end of November and weather has been warm and comfortable for us and a great time to go.