We spent a week on Peak's Island with our group of 4 adults and 1.5 year old twins in June. If anything, the house is even more charming in person and the surrounding property was full of gorgeous plants and flowers and backs up to the forest. The house is at the end of a quiet, dead-end road with incredibly kind neighbors across the drive. You can hear the ocean waves from inside the house when the windows are open and you have an amazing view of the water from the wrap around, covered front porch! Every corner of the house felt lovingly cared for and thoughtfully arranged. There was a pack n play and a high chair provided at the house (though we brought our own since we have twins!) and we found great spots to take a picnic and splash around in the shallow tide pools with our toddlers a ways down on the rocky beach. There are some steep staircases in the house, however, so if you have little crawlers / new walkers, you'll just need to keep an eye on them. We had no problems with that.
One of our other favorite things about the house was the outdoor shower! We all preferred it to the indoor shower option.
We drove and had our car with us, but it costs $70 round trip to ferry the car to and from the island so we left the car on the island all week and only drove it to get to the ferry if we wanted to go into Portland, which we did several times and explored on foot. There were plenty of walkable shops, restaurants, coffee shops, etc from the Casco Bay ferry dock in Portland so not having our car on those days wasn't much of an issue. We loved our entire stay and found the island to be full of charm, gorgeous houses and beaches, and friendly people. Would go back in a heartbeat!