Batchelor button is a good choice because it can take a light frost, and in many parts of 5b the chances of a frost by mid-October are better than slight.

I'd add a mix of double calendula -- the old Pacific Beauty mix would be fine. The flowers are much smaller than sunflowers, but they aren't tiny, they cover some of the color range you're looking for and they're very frost hardy.

You don't have to start either of these early. I'd wait to start the batchelor's buttons until summer, so they won't exhaust themselves by October. The calendula seem to bloom and bloom. Plant a goodly number of each.

You might think of something like a double feverfew to give you a white filler. They're also cold-hardy.

Rudbeckias can last well into October. They can take a light frost. Calendulas are very frost hardy, but they need support if you want tall, straight stems. Snapdragons are extremely hardly, in fact they are considered a tender perennial. They are one of my all-time favorites for cutflowers.