Hi Percys,
You defiantly picked a good fishing spot. I have been there several times during the open water season and each time has been fantastic.
I only keep a couple to take home for a meal but over one weekend, I and two other angles caught 50 Northern Pike, the average around 3-4 lbs and a couple pushing 8 or 9 plus I lost 2 Monsters that I am not sure how big, one I lost at the boat and the second never moved him from the bottom. It also has a healthy perch fishery and an odd walleye are now being caught. I have never tried it in winter but have friends there and they say they can catch fairly consistently in winter.
As far as getting on the lake you can access it by driving to main street Big River and turn west and follow the street right to the lake. Another access would be a camp site that is half way up the lake, it will be to your left. Like galvanizednail said Cowan lake has a fair amount of current, caution is advised, defiantly do some test drills before setting out onto the lake, also watch the beaver dams, the ice around them will be very thin. Also when fishing the bottom is littered with logs and stumps so may loose a lure or two on them.
As for lures really anything will work, but I would recommend trying larger lures like a large rubber shad,curly tail, or smelt should work for the big bruisers that prowl those waters.
good luck this weekend and have a blast!!
Water Wolf