Third week of June through mid-August is usually very crowded with week of July 4 being the most crowded; third week of June would just be a bit lighter than week after the July 4 week; also since you are planning two weeks, that last week in June will actually start the build-up to the huge, huge July 4 crowd. Last two weeks of August are lighter than any of the summer vacation weeks (actual lightest "summer" weeks -- and some of the lightest weeks of the year -- are anytime in Sep after the Labor Day weekend). Don't know when or if you have been before. If a comparison helps: the two Easter weeks and Christmas week are the most crowded (non-fastpass lines at popular rides get to over 2 hours and some 3); July 4 week comes next being slightly under those; and President's week and all those other weeks between mid-June and mid-August are next on the list but still significantly less than Easter or Christmas. In any event, if you choose any week between mid-June and mid-August other than July 4, you should expect non-fastpass wait times at popular rides to range from 60 to 90 minutes all day and night except early morning.