that's an interesting question. First, I think the AP rate will be lower startting 7/5. The rule is that the AP rate is good for CHECK-INS between 7/5 - 8/28 (at least that's what I think the end date is going to be this time per the rumors). I don't think so - I think you're stuck with whatever the rate is on your check-in date UNLESS you get an exception from someone....who I don't know.
Why don't you stay off-site at a cheap hotel the first night and check into Disney on the 5th? We wanted to go 7/2 - but decided against it for this very reason - to get the AP discount during VALUE season. Which is 7/5 at deluxe resorts.
PamNC