I love the place and have been going there annually since 2004. Pellston makes a good fuel stop. There are landing fees at MCD. You'll get a carriage taxi from the airport for about $7/person. You'll definitely be inundated with fudge places, and it is good.
As Mike said, the tours are nice, and it should be a wonderful bike ride after that, since you'll know where you're going. Get at least 3 speeds. Next to the Lakewiew hotel on the west end of the main street is a place that has 6 speeds, or a couple of places also have mountain bikes or tandem bikes.
You can do horseback riding for about $30/hour at a couple of places. You can get a guide at no additional charge if you want.
If you do dinner or even an evening stroll at the Grand Hotel, be aware that there is a derss code which includes at least a jacket, maybe a tie. Also note that there is an admission fee to the Grand Hotel if you're not staying there. Leslie says that even walking on their porch/street requires payment of that fee.