I would drive to Quebec City and then Tadoussac. Spend some time there whale watching and seeing the Saguenay Fjord. Then take the ferry from Les Escoumins to Trois Pistoles - there are often beluga whales right along the boat. Then go to Mont Joli and cross the Gaspe on 132. Stay over in Campbellton. Go on to Miramichi and then connect at Shediac to the Trans Canada to PEI. Return to Montreal via Moncton and Riviere Du Loupe. The train also goes to Campbellton from Montreal. Look for seat sales on VIA. (From the VIA Rail site "To be among the first to find out about new seat sales, sign up to receive our e-letter.And don't forget to check out our Express deals. You can save 50 % or more on select eastern or western destinations.")