NJ through New England - Campground Ideas Needed

[I[how many days to do Acadia, would 4-5 be too few, we don't need to hike every trail.

Definitely not too few, possibly leaning towards too many, depending on what you want to do. It's not a big park but if you plan on biking, hiking, horseback riding, driving the loop road, going up to Cadillac Mounting and/or hanging on Sand Beach (be forewarned the water is COLD) you can easily fill up 4 or 5 days. If you are more a "casual observer" then 2 would probably be fine.