Hi Bluebutterfly,
I've been watching to see if you had any replies to your query. I think it's rather a difficult one because you're working in shade and you want to stick to native plants which is a great idea.So right there you're limited to what will grow. Any flowering bushes we have growing in this area are mostly fruit bushes so they have a limited springtime showy period.(After last weekend, I think any bushes would have had second thoughts about flowering any time) As well, most fruiting bushes like sun. I live in a wooded area and discovered some time ago that you can work with nature, but not against it when it comes to gardening. If I were you, I would take a wander around the area and see what's growing there and perhaps try and transplant some plants as long as they aren't a protected species. A driveway lined with ferns would look nice, if not showy. If you're willing to spend a few $ there are some knowledgeable folks at the Garden Centre in Temagami who might be able to give you some ideas. Good luck in your search.

Hi highbush cranberries grow well in this area(Northern Ontario) They have berries in the fall and look very pretty.

What about chokecherries or a dogwood. Don't know if they are native to your beautiful friendly area but they do well in Manitoba - zone 2/3
Inanda