I've only been the 1st-3rd weeks....while kids are still out for summer. I can honestly say I will never go back in the summer. Last time was January & it was heaven - seriously. Walked onto every ride, didn't use FP once.
BUT since kids MAY be in school by late Aug/Early Sept (ours start 8/10!!)....it might be a lighter crowd. I'm curious to see what others say....
August will be packed of course. The first week of September is the last major holiday before school starts locally. I did WDW and Labor Day was packed and the following Tuesday was an empty park so to speak. Same for DLR.
Use online databases and go early as you can to the parks. Use priority dining when you can and to save money some places have split plate meals. EArly dining will help and avoid the noon crowds for example. It will take lots of planning and a willingness to alter plans as needed.