We have a 9:05am ADR too!! We are planning, or should I say hoping, that they let us in at 8:30 so we can try to get seated early. I figure even if they don't let us in until 8:45, we can still get that picture in front of the castle before everyone else gets let in!
FWIW, in all our early ADRs at Magic Kingdom, nobody has ever checked our reservation. I'm sure that may not be the norm, but we always try to be super early for our morning ADRs and are always let in.