HI there. I've been tent camping extensively in Maine with my wife for a lot of years. To meet your goals, you might look into two specific campgrounds that won't require an all day drive from the NH border. As mentioned, the weather up there in September-October is gorgeous. There can be warm days but there are more days with that crisp chill in the air that makes camping in the Maine woods so magical. You won't be able to get the smell out of your head and that's why they sell so many pillows of the leaf litter up there so you can bring it home! Anyway, I'd recommend these two options:
1) Check out "Wolf's Neck" campground located on the ocean in Freeport, ME. It offers enough amenities to make your wife comfortable. It's located in conjunction with a farm. You can read about it here. We'll actually be there on Sept 21-23rd to shake out a new tent rig we moved up into. I've driven through there in the past but never camped there but the sites will be deliciously next to the ocean and, in september, the bulk of the tourists won't be around as much as over the summer.
https://www.freeportcamping.com/
2) If you'd like to go a bit further up on the coast, you can go to the Camden area as suggested by the other poster up top. There is a state park there called "Camden Hills State Park".
https://www1.maine.gov/cgi-bin/onlin....pl?park_id=14
Camden is quintessential Maine in just about every category. Not to say that other locations aren't as gorgeous or breathtaking at all. It's just that Camden has it all. You should be able to book passage on the trips you're looking for. The camping is for-real woods camping but I don't believe there are hookups. We've camped there but it's been a while. The town is just down the road. Park and enjoy the zillions of places to eat and poke and check out the boat scene.
Have fun!