Well, there are some things to keep in mind.
Canada is sparsely populated, if you’re driving, take your time, otherwise you won’t enjoy yourself much. The scenery is nice, but trees get tiresome after awhile. At the same time though, unless you want to ‘get away from it all’ there is sort of a straight line of major cities from Toronto to NB, which can make the route easy. Here is what I would suggest as the typical go.
You can do the drive from Ottawa to Halifax in a day if you don’t need sleep (add about 5 hours from Toronto). If I was you I would start in Toronto and maybe do a swing of Niagara Falls if you have never seen them (from the Canadian side of course 
) then travel up through Kingston and check out Fort Henry (as with everything else I will mention, check the web for special events, like recreations and the like, they can make and break a trip obviously) Then it is up to Ottawa. You can skip it if you want, a good many people find the city boring, but it’s home and I love it. Ottawa’s a pub city, with great museums (check out the new war museum), Parliament Hill and a fairly active Irish Community (see city guide). Ottawa is surrounded by the Ottawa Valley, with some older towns, picturesque but whether they’re worth the trouble, that’s a matter of taste.
Ottawa is on the Ontario-Quebec border and you are looking at 2 hours to Montreal. Again, you’re looking at very scenic land, nice hills if you’re wanting a hike. Don’t know what your budget is like, but checkout some of the resorts if you need to relax a bit. Montreal is a fun city, and there’s bunches to see and do. Check out Grosse Ile, old Quarantine station for the port of Montreal and mass grave of Irish immigrants. Quebec City is about 3 hours from Montreal, and is the most beautiful city in North America. If you’re driving through Quebec, you pretty much need to stop in Quebec City. From there you can go up the St. Lawrence, maybe even see some whales. Moncton is a good base to do the Maritimes. Nova Scotia is just South-East, go to Halifax (plan it with the annual military tattoo (sp?) if you can. I love Halifax, but it is rather small, I think it can be done rather quickly. Couple hours from Halifax up into Cape Breton. Sidney is a dump, but Cape Bretoners are the nicest people on the continent so stop if you’d like. The Highlands are where you want to go. Make sure your car is up to it, then head for the Cabot Trail. If you like “Scotch” you can check out Glen Breton distillery. Like I said, if Scotland is what does it for you, you’ll love the Cape Breton highlands.
PEI can be reached by ferry from New Brunswick (St. John?) or from Confederation Bridge, which would be cool to go over (http://www.confederationbridge.com/bridge/bridge.aspx?pageid=2&lang=en). I didn’t find PEI very exciting, but I was young. Lots of Lobster though b’ye, and super nice beaches (Charlottetown is historically significant as well). If you have the time, try to get to St. John’s, it would probably be worth it.
That’s a real short go over… REAL short. Like any country, you should get off the beaten track, and in Canada that means quite alot. For your interests, Irish and Scottish culture is not too difficult to come buy. Canada has four founding nations and those are two of them, so each major city has at least some of their presence. It’s a big country and there is lots to see and do. Any specific questions and I’m sure myself or one of the other Canadian Chiffers will be able to help.
