You got lots of great advice. Also no to May, if you go in June time your visit for the lilac festival. But if it were me and your timing is flexible, visit in September. I love September, the weather is great and most of the crowds are gone.
No matter when you visit, don’t forget jeans and a sweatshirt, the island and northern Michigan can get chilly. I made that mistake years ago never again.
I have a suggestion, rather than flying into Detroit, fly into Traverse City. The ride from Detroit to Mackinac is pretty boring. If you fly into TC, you can explore Sleeping Bear Dunes (one of the most beautiful places). Drive along Lake Michigan, the scenery is so pretty. Explore Charlevoix and Petoskey. Make the drive up to Harbor Springs. I do like Greenfield Village and you could stop in Frakenmuth for chicken dinner, but if it were me, I would explore Northern Michigan and save Detroit for another visit.
I would take the ferry from St. Ignace. As a first time visitor, go across the bridge!
I am no expert on the island, my H is not a fan. He’s being ridiculous but it’s his line in the sand. So I’ve only been a couple of times. When I’ve gone, we’ve always rented bikes and biked around the island, I think it’s 6 miles. If you don’t stay at the Grand, you have to pay to visit. So we ride bikes, have lunch at the Pink Pony, buy fudge.
If you have other questions about Northern Michigan, I’ll be glad to try and answer.
One other thing about the weather, we have good ice coverage on the Great Lakes this year. That means spring will be cool. Last year we had little ice coverage so the spring was warmer but I don’t expect that this year.
