That's a great time to travel. I live in northern NY on the Vermont border and have noticed fall foliage season is later each year. I'd take RT. 2 west from Bangor through upper Maine into northern NH and VT. Likely very nice leaf peeping and scenic. Cross Lake Champlain to the Adirondacks and then head south on I81 or rt 15 through PA. Great tips about Gettysburgh and then on to Blueridge parkway and western Virginia and Ashville region of NC. No major cities, lots of hiking and biking areas, sounds like fun. Most State Parks in New England and NY close by Columbus Day so you'll need to search out private campgrounds, but it's also really easy to just pull into forest roads, boat launches , ski areas etc.
That's what I'd do, but its hard to go wrong otherwise. I just hate the NY City area down to Washington DC and would avoid those areas if possible.