The Lake Erie Islands are a great spot for entertainment, history, and family fun in the summer months. Each island is unique and offers something different. You just have to decide which one is the perfect match for your particular family!
Kelleys Island is great for natural history, with its glacial grooves. They are quite interesting to see. The island there is more low key and laid back. Mostly families.
Middle Bass Island is mostly residential and is even more laid back. Not much history except for Lonz Winery, but there is a new state marina, Hazards, a couple airports, and a couple bars/stores to visit. Mostly residential.
North Bass Island is rustic, and you have to have your own means to get there if you want to explore. Not usually offered as a tourist destination.
Pelee Island is Canadian, so unless you bring your passport, you probably don't need any more info on this one.
Rattlesnake Island is a privately owned island for members only. Fun rumors abound about smuggling, gangsters, mafia, Russian oligarchs, foreign workers for the summer, etc. In truth, it is a small grouping of expensive houses on a members only island with high dues, a golf course (which doubles as a landing strip, you just have to play through!), and a small marina for private boats.
Oh, and there is also South Bass Island, also known incorrectly as Put-In-Bay. This is the most populated, most well known, most visited, most touristy island of the bunch. Lots to do and see and visit and view and explore and eat and drink and be entertained. Huge entertainment schedule each summer. Lots of culinary destinations. Golf carts and bicycles as far as the eye can see. Beautiful downtown marina. Many historic and touristy sights. And a big National Monument you can go to the top of and view neighboring islands, states, and even countries on a really clear day.
For kids, I usually recommend Kelley's instead of PIB. PIB is party central during the summer and not really for kids - too many bars, etc.. The kids are a little young to appreciate the Perry Monument.
Kelley's has the Glacial Grooves(Oh. Hist. Soc. property) but across the road is a great park with great beach. In the village, are some nice shops and some pictographs on a large boulder to see. Much more laid back, more family friendly. Great ferry ride.
While South Bass aka Put-In-Bay is more of a party atmosphere, there are still a lot of family friendly activities that aren't to be missed. The partiers mostly stay downtown, and things don't get too crazy until the evening. Perry's monument and the National Historic Park visitors center. Perry's Cave. Crystal Cave. The Butterfly house. The Islands Nature and Wildlife Center. And you can rent watercraft.
Kelleys is nice too. Laid back, less to do. The glacial grooves are cool, but I'm a geologist, so....
The state park has a nice beach. There's cute shops and mini golf.
You can rent bikes or carts on either island. Personally, I'd look into island hopping! From Sandusky, you can take a Goodtime I cruise out of Sandusky. The boat stops for a few hours at Kelleys, and then you board the boat and it takes you to South Bass for a few more hours. Then you head back to Sandusky.
You can do a similar island hopping with the Jet Express out of Sandusky as well, but it's more expensive. You aren't beholden to a set schedule either.
I take my elementary school-aged child to PIB all the time. There are tons of things to do for families and kids, and there's a great playground right in the center of town. Between the candy shop and ice cream places, Butterfly House, Perry's Cave, putt-putt golf, the state park, Perry's lighthouse and lots of places to eat, I have never had a problem bringing my kid to the island.