My first Atlantic Salmon trip was to the Margaree River 30 years ago. I doubt the campground I stayed at is still there. Just Google Margaree River and Cape Breton Islands and you'll find plenty of information on the angling and accommodations.
There are no Char in Nova Scotia as far I know. You'll have to go further north to New Foundland or Labrador.
I have caught Arctic Char in both Alaska and Labrador. Quit frankly I wouldn't travel that far just to target that species. They're not worth it. Fight like dead salmon.
Brook trout, sea run Brook trout and Atlantic salmon is what you're after. By all means get yourself a guide for at least one day. Guides are dirt cheap in Canada as compared to the US. $150.00 a day will get you a good one. Good luck! You're going to love it up there. Especially in the Fall!