Buy a one-way ticket from Portland to Peaks Island, since the way back is free.
Biking is the best way to see the island, but you can also rent a golf cart (which is best if you want the shade). There are no public bathrooms since it's basically a small town; plan on making a food stop at a restaurant so you can use the facilities.
Since this is an outdoor activity, head out in the morning or around lunchtime to give yourself ample time to explore the island.
The island is beautiful in spring and summer, and even early fall.
Children under 5 ride the ferry for free.
This little day trip from Portland, Maine, to Peaks Island is a 17-minute ferry ride. It promises relaxing outdoor fun with the whole family. Begin your day by heading down to the Casco Bay Lines. Check out the Waterfront District on your way down to the ferry to Peaks Island. Once on the island, grab a bike at Brad’s Bike Rental and Repair and head off on your trip around the area. Seeing the island by bike offers the best options for taking in all the gorgeous nature and vistas Peaks Island has to offer. For those who have a sweet tooth, stop off at the little roadside honey stand for a souvenir. This stand operates on the honor system; drop in some money and take a jar of honey. Next, pay a visit to the The Inn on Peaks Island; not only is it one of the only bathroom options, you can also satisfy your hunger pangs with some local fare here. Continue around the island and work up a bit more of an appetite before heading to Milly’s Skillet. This little food shack is well known and popular. And since you’re in Maine, you shouldn’t hesitate to get your fill of lobster rolls or fish tacos while you can. Next, finish the day with something sweet for the kids (or dessert-craving moms and dads) at Down Front and grab some ice cream to polish off a great little adventure.