One can indeed interpret it either way. I have contacted Choice to get the official answer.

Regarding the Park&Fly rate, I have no information one way or the other. Choice has traditionally allowed just about any rate avaiable on the website to count, but special, hotel-unique rates often do not.

Your best bet is to:

1. Call the hotel and ask them, and get the rate code (typically 3-4 letters)
2. Call Choice and ask them if that rate will qualify.

I doubt if many foks here (if any) have been in this particular situation before.

Edit: Upon re-reading your question, it's pretty clear that in order to count, stays must start on or after Sept. 1