Cathy: For a bit of comparison, the Sanfermines in Pamplona "start" on the 6th, and the special event in the plaza del ayuntamiento is great, but the first encierro doesn't go until the 7th...that being said, I think you'll miss something if you're not in Olite on the 13th, but I think that there will be much to see on the other days, too.
The parador is beautiful. It was the former residence of royalty. Sancho el Fuerte started it with a castle in the 12th C., and Carlos III of Navarra completed it with expansion in the 14th and 15th. It is an incredible place and surrounding old town adds to the flavor.
Pamplona is just up the autopista from Olite, so you should be able to find regular buses from O to P. For me, Pamplona is always worth the visit. September offers a bit of a respite from the hot summer sun in Pamplona (but not too much yet), and visiting the casco viejo and ciudadela park is something I'll never tire of...
Unless you're a winebibber, Olite's festival should give you what you need in the arena of fall harvest festivals, wine festivals, etc. There are those who contend that the Rioja region is Spain's finest for wine, however, so you can plan according to your own taste.
P.S. If you don't post on your trip when you get back, none of us will ever speak to you again!
Enjoy!!!, and if you're in SoCal, we all need to get together this fall and see your pictures when you get back!