The White Mountains of New Hampshire- Camping
Here is a good place to start. If by New England you intend on focusing on NH. The area between Lake Winnepesaukee and Franconia Notch is a nice stretch of scenery as well as having plenty of things to do, if you tire of leaf peeping. I've stayed at Meredith woods (very quiet and private sites) as well as The White Mountains of New Hampshire- Meredith
Harbor Hill. Most of the campgrounds will meet your needs and won't be 5 star resorts, but the people are friendly and chances are you'll be out in the area during the day. I've also stayed at a place called Branch Brook Campground > Home
Branch Brook, which has limited power, but if your up there for the foliage Sept-Oct, you will not need AC. You'll need to start booking sites soon as the camp grounds to get full, especially up through the Columbus day weekend.