Having read the two replies thus far, I started checking the availability of accommodation at Yellowstone. It would seem that the park itself is full on the night of August 1. Oops. I broadened the search and found an establishment in West Yellowstone which, according to my computer, had ONE room remaining.
Observing they require no cancellation fee and no prepayment was required, I pressed the button and the room is ours. It is very much over budget, but now at least I can rest easy while seeing if I can find something less pricey.
The Labor Day weekend should see me in Ocracoke, OBX. I will get onto that this evening; but for the rest of it, I will retain flexibility.
Thanks for the advice, chaps; much appreciated!