Your response sounds exactly on-pitch, Knute-- I'd maybe follow it up with a phone call if this is still within the contract year (it might be, if it's the week after-- and in some districts, there is staffing in the office for a few weeks during the summer).
I agree that a fall 504 meeting as a routine thing is a great idea-- but changes can happen when they need to. Clearly, a teacher who knew your child in a classroom setting saw genuine needs, and took the time to outline accommodations for classroom use. That's HUGE-- because nobody but a classroom teacher is really in much of a position to say what can/can't happen in the flow of a classroom-- that's why it's such a good idea to have teachers as part of the 504 team.
Good luck.
