Fall weather in the NW can be very nice. The hot weather is over and the rain doesn't set in until mid October.
You will be crossing the Rockies and Cascade mountains, possibly others depending on the route. Snow can hit the passes by mid October, but doesn't start sticking for a few weeks after that.
There are lots of hilly curvy roads out here, perfectly safe if driven properly. We natives do it all the time and think nothing of it.
My only concern would be you tow vehicle. I personally would never consider a Tundra for towing any 5r.