S.H.
Let's see... so much to do!!! Mackinac is one of my favorite places in the world! In the City, there is a laser light show every night at dusk and Dixie Saloon has the best fish and chips. There are two water parks: one is for the public and the other is for guests of a bunch of hotels. Mill Creek is fantastic and has trails to walk, adventure trail (climbing wall, zip line, and high canopy walk). Check out these websites for coupons: http://www.mackinaw-city.com/ & http://www.mackinacparks.com/ . Also, the first website should have coupons and schedules for the ferry rides to the island. Ride on the bottom in the morning if the air is still chilly, but ride on top at night (hold on tight to loose items and you may get wet!). You can bring your own bikes for a small fee or rent them when you are on the island. The fort on the island is great and there are plenty of maps when you get there for bike tours. You could also pay to take a horse carriage tour. Definitely check out the Grand Hotel (you won't be allowed in unless you are a guest and in dress code, but you can get close enough for good pics and a good view). As you go to the hotel, you will pass the island school, which has a playground. Also, check out this website, cuz there are just too many things to do on the island for me to list here! http://www.mackinacisland.org/ .
Have fun!!!