As a born-and-bred Quebecoise here, Montreal is the best place in all of North America, in my complete and unabashedly biased opinion. Walks on Mont Royal, Old Port, Old Montreal, Plateau, Mile End ...
And the food ... try St. Viateur and Fairmount bagel bakeries and argue about which one you prefer. Line up at Schwartz's on the Main (St-Laurent) and have a smoked meat sandwich with an order or half-sour pickles and a cherry coke. Little Italy for amazing Italian food, and the church (Madonna Della Difesa) on Dante Street that has a fresco of Mussolini on the ceiling. It was covered up with a tarp during WWII. Have some biscotti or cannoli and an espresso at one of the cafes on Dante when you're done.
If you want restaurant recommendations, we've got plenty, just ask.
I love the Maritimes too. PEI for the beaches. Nova Scotia is a fab place - hopefully you can tour the whole coast. Stop for scallops in Digby, watch the tides in the Bay of Fundy, hang out in Lunenburg (old town, a UNESCO heritage site, and home of the Bluenose II). Halifax is a really cool place to visit too. The harbour area is full of life. New Brunswick is very welcoming - it's been years since I was there but I have fond memories of Fredricton and Moncton.
Newfoundland is awesome and also VERY expensive. Before you travel to the Rock, bring as much non-perishable food as you can carry. Prices are close to double what they are on the mainland. If you like to hike, Grosse Morne National Park in Cornerbrook is a must, or you can visit the Viking settlements in L'Anse Aux Meadows (a great franglais name) at the upper tip of the island, or Point Rose, which is closer to Port Aux Basques, where the ferry from the mainland docks. St. John's is also really nice. You might also try to get to St-Pierre and Miquelon, which are two islands off the south coast that are actually a part of France.
You will meet some of the friendliest people on the planet in the Maritimes. Have fun!!