Spent 4 days at the Blue Heron this summer and were not disappointed! We were coming from Montreal, so I was a little nervous about the 5+ hour drive with 4 adults and a 3 year old. Once we got there all our tension just disappeared. We were not disappointed with the cabin - it was just as described and perfect for us. Allison was so generous, leaving us a toddler bed, stroller, booster seat and a big box of Lego. Not having to schlep that stuff with us was a big help! The cabin is rustic, but clean and fully equipped.
The beach was sandy and shallow - good for little swimmers. Kayaks were fun to get away for a bit and explore the surroundings. Plenty of relaxing areas, but still not so isolated that you can't meet someone new at the campfire. We shared our s'mores with two nice families from New Jersey.
The one day it rained we drove 1 hour and spent the day Portland at the Children's Museum and then headed for lobster at Demillo's. Then we stopped at Freeport outlets on our way back. Everybody had fun despite the torrential rain!
Grocery stores are not far, so we didn't have to worry about what was permissible at the border. And wifi helped to locate them.
I've already told everyone I know with young kids about this place!