I use to live and work on madeline seasonally, actually heading up there this weekend. It is my favorite place, my wife and I miss it all of the time.
Anyways, as for shore fishing not much availabe for great lakes catches this time of year from shore, but the lagoon @ the town part offers good pike fishing all year long. There are canoe rentlas available onsite, and within short paddling distance you should be able to catch some fish, probably only small ones, sometimes the big girls that come in from the lake to spawn in the spring will hang around ….and ya just never know. The pedigree of pike that live in lake superior are pretty darn awesome, have seen and caught some pretty awesome fish in the lagoon and in the harbor. Spoons seem to always uot perform just about everything.
As for family/kids fun are you staying on the Island or just day tripping?
The town park beach is very beautiful, long stretch of beach. Joni’s beach in town usually has the best water for swimming, the north end of Isalnd (town park and State park has much cooler water temps.
There are bikes and motor scooters in town to rent, but really not worth it in reality, it is an awfully big island and is best navigated by car.
The apostle islands are amazingly beautiful, and Madeline Island is a really cool place, but it is not line with fudge shops and the like as Mackinac is, for that reason some are not that impressed.
Let me know if day trip or overnight and I can provide additional insight to your trip, is this your first visit?