Not all school districts will be back in session by the end of August. Some schools don't go back until September. And there are a lot of districts that affect crowds at DLR: Southern CA, Northern CA, AZ, NV, UT, OR, WA. You get the picture. By the end of August, DLR traditionally moves to the non-peak schedule, which means shorter hours, more refurbs, lower staffing, less entertainment, nighttime entertainment on weekends only, etc. HM will be down for the Halloween overlay installation. And the return of the lower APs to DL will definitely affect crowd patterns. I would choose July when DLR will be totally prepared for the crowds and the lower APs will be blocked from DL. You'll have longer hours, rides running at full capacity, more staffing, more entertainment, nighttime entertainment every night, etc. This makes a very big difference in how smoothly things run in the parks. It may be crowded, but you won't feel it as much when the parks are prepared to handle it. With good planning and preparation, lots of patience, and a positive attitude, you'll have a great trip!
As for SWGE, by July, you'll have had over a month to read the updates here on how to handle the crowds and what the best strategies are. Keep up with the threads here and you'll be a pro by the time of your trip!