We are traveling during this same time period (arrive on 8/26 and depart for a cruise on 9/1). This will be our third time traveling during this time period.
We have found the crowds to be very manageable for the most part. I always have a touring plan, but we have found that we could be fairly flexible with our plans and still do as much as we wanted.
Two main areas we have found that we could not be flexible was dining TS and MK. I always plan our dining well in advance (party of 7 and we have done free dining time, so it is important).
Also, we find it necessary to have a good touring plan for MK and that deviating from the plans can mean long waits (not necessarily missing things, just takes longer and larger crowds).