I have a pass to the fort on the island, the fort on the mainland and Discovery Park at Mill Creek. I can mail it to you, for free. It's a family membership good till October, but they never once checked id's with it. For Discovery Park you can do the treetop thing with zip line and rock wall for $5 a person more, but otherwise the membership covers admission.
We just went at the start of August.
Go into any hotel and ask if they have coupons for one of the ferries. You can use the coupon at any ferry, they all take competitor coupons.
Do not eat the Dixie Saloon. Way overpriced. Poor selection, smoke filled and crowded.
Buy fudge on the main land, it's half the price. We got our at Petoskey Stone Creamery.
If you want a nice day trip head North into the Upper Penisula and go about an hour or two north to the Oswald Bear Ranch. It was great, I got my picture taken with the male bears right behind me - I was inside the cage and they were about 10 ft away eating. We also did a family picture with a bear cub, I fed him fruit loops while the owner took our picture. That day we also did Tahquamenon Falls - the upper falls are very pretty but the lower falls are really neat. You rent a row boat and row over to the island which is surrounded by the falls. Bring towels and wear swimsuits and water shoes. You can walk right IN the waterfalls and it is so neat. Very memorable. The resturant at the Upper Falls was very good.
Mackinaw Island - we ate at Village Inn. That was a great meal and not overpriced. We also went to the butterfly house and honestly the one at Brookfield Zoo is much better so I would skip it. Also all the town is owned by just a few people, so don't listen to recommendations. All the people working are basically paid to recommend set places. We did a horse drawn carriage ride around the island. I wish we could have done actual horse riding but you had to be 9 I think and Elise is only 6. I think renting a buggy on your own would be neat too, but the guides were great on the carriage ride. We had burgers and great BLT's at Mighty Mac Hamburgers. The BLT's was enough for both my kids to share.
Mackinac City - we liked the food and atmosphere at the Historic Depot. We also ate at the Pancake Chef and it was good food.
On the way home we stopped at Empire and did the Sleeping Bear Dunes. AMAZING. This is a must do. The scenic drive is neat too, worth doing as well.
We headed south along Lake Michigan trying to find a beach and finally found one off of Lake Michigan Road off of 22. This had a nice parking lot and a river that ran along the lake so that you had warm swimming water as well as the lake. There were Petosky stones all along there and my 10 yr old loved finding them. Take a look in the gift shops in Mackinaw so you know what they look like unfinished (look at the unpolished side).
We also stopped in Muskegon on the way back home and they had a great public beack by the submarine museum down by the lake. My husband went to the sub while I took the kids to the beach. (This was the second sub tour of the trip after all).
If you want any more info or want that membership ticket, let me know.