Mackinac Island offers a relaxing respite from hectic, over-scheduled family life. There's little rushing around (the entire island is only eight miles circumference!), a leisurely pace (it's filled mostly with summer vacationers), and no traffic -- cars aren't allowed on the island; you'll leave yours at the ferry on the mainland. You'll appreciate Mackinac Island's Victorian architecture and its historical sites, and your kids will especially love the horse-drawn carriage rides, and biking, skating or walking around town without you worrying about traffic.
Mackinac Island is in upper Michigan making springs slushy and cool, and winters just...well, cold. But summer and fall are both great times to go. Mid-fall may be the optimal time, when temperatures are just warm enough to be comfortable without being too hot for walking around outside all day. It's not as crowded as in the summer, and accommodations are often less expensive, plus, you'll have a chance to see the gorgeous fall colors as the leaves change.
Winter is a decidedly difficult time to visit. Ferries to the island stop running once the temperatures drop.
The average temperatures during May to September range from a low of 52 degrees to a high of 75. A light jacket is a good idea during any of those months -- even if it's warm during the day, you may find that it's cooler in the evening (or during your ferry ride to and from the island). Get more weather info.
The vast majority of tourists get to Mackinac Island via ferry (a 15-to-20-minute ride), since there are no cars allowed on the island. You'll park at Mackinaw City, MI, or St. Ignace, MI. Parking at the ferries is usually free for day-trippers, and secured parking at a cost is available for those staying a few days. Visit the following ferry websites for prices and departure details: Arnold Transit Company, Shepler's, Star Line Ferry.
Since you can't drive on the Island, your options are limited to walking, biking, or getting around by horse (either on one or behind one). You find plenty of bike rental options, horse-drawn carriage tours, and you can even rent a horse for riding on trails. Visit MackinacIsland.org for more information.
Mackinac Island has a few exciting annual festivals, but keep in mind that you'll have to contend with bigger crowds and pricier hotel rooms.
MackinacIsland.org is the official site of Mackinac Island, and has information on everything from accommodations to festivals to shopping and eating.