Dorset is on Lake of Bays and there is little in the way of official organized camp sites on the lake. The main towns are Dwight, Dorset and Baysville. Dwight is accessed off of Hwy. 60. Both Dorset and Baysville are accessed off Hwy. 117. If you want to wait until you actually get there, you will find a tourist office right on the highway in the town of Baysville. Both towns have pretty much everything that you need. Fishing is good in the lake. Mainly smallmouth, lake trout and pike. There is a lodge on the lake named Beauview Lodge. I have no idea if they have camping facilities, but they may be able to point you in the right direction. All of the towns provide easy access to Huntsville as well.
I hope this helps.