I've been to Quebec, but not for a very long time. You will have language problems outside of Montreal, but don't let that stop you. You should definitely see Quebec City. Take one of those tours in a horse-drawn buggy if you can. The way the drivers get them through traffic is really cool.
I can't imagine going to Montreal without seeing an Expos game, but they are gone, so you can...hang around the peeler bars, I guess.
In Ottawa go see the Parliament Buidlings. If they are sitting, watch a session of Question Period...it's way better than monkeys at the zoo, or even professional wrestling. The Rideau Canal has (or used to have) a couple of old mills etc on it. You can drive down Sussex Drive. You can check out the GG's Mansion.
If you are there in the fall, definitely go check out the Gatineau...take a camera. Our trees in the west don't have that many colours.
You can go see my old house. I haven't lived there since 1977, but the address is 917 Tavistock Rd. Not sure why I still remember that. I wonder if it's still orange?
Lemmee see, what else? The whole area is actually full of historical sites. If you like those kinds of things, you won't be bored. If you go in the summer, be ready for some really unreasonable humidity.