I attended the LA PEPC in June and during my meeting with the HR rep they offered me a July class date. I felt the same way as you and wanted more time to clean up loose ends and enjoy more of the summer with the family. They had no problem with this and offered me classes through Sept. When my HR rep emailed me for some information for my FOL he actually tried to put me into a July class date again. I asked him about later class dates and he had no problem assigning me into the 8 Sept. class.
I agree w/Bloomer, I was also at the LA PEPC, but for En Route and the latest class date available was August 19th. When I asked for a later class she was fine with it, but my current issue is the new class schedule doesn't come out until August sometime and I have no idea what the next schedule will look like. You may have to later than planned but I agree w/Bloomer that it shouldn't be a problem.
to take it one step further in the process, I was able to move my class date back from June 20th to August 19th after receiving my FOL about two weeks before I had to leave. I don't think you'll have a problem at all.