Jim and Trish,
I haven't been up there this time of year, but you can go to www.weatherunderground.com,
put in Bangor, ME and click Trip Planner. You can then enter the dates of your stay and it will give you a weather 'forecast' based on data going back to 1993.
We stayed at the Narrows Too campground in Trenton, ME. From the website, it looks like it was just remodeled last year. Be careful as some of the campgrounds there close in mid-Oct.
Bar Harbor and Acadia are fantastic. A must stop is Jordan Pond for 'popovers' with a scoop of ice cream inside. Beware of the 'moose dropping' ice cream (actually Milk Duds) and the lobster-flavored ice cream. If you want a great hike, try the 'Perpendicular Trail' on Mansell Mt. (to work off all the ice cream!)