bex,
To begin with, welcome to the Boards! I have a few comments to on some of the places you listed in your Itinerary.
You might consider meeting your friend in Scotland, as there are good flights from Canada with
Air Canada, Air Transat or Canadian Affair. As you'll be with family, it would probably be a nicer place to get over jet lag.
On your way south to London, you might consider a stop in York for a day or two. It's a wonderful and historic city, and there's a good Hostel there in an old mansion.
Plan at least four or five days in London, as there's LOTS to see! London can be an expensive city, but many of the public Museums and other sights are free (although not all).
Take the
EuroStar from London to Paris. It's a bit expensive, but I believe it is possible to get some discounts. You might consider Bruges instead of Brussels (unless there's a specific reason you want to visit Brussels?).
I'd recommend only two or three days in Amsterdam (
herrbert can provide more specific advice on that).
For the south of France, I'd suggest using Nice as a "home base". There are some wonderful galleries and other sights there. It's easy to see Monaco or Villefranche as a day trip (as I recall, the Bus fare is only €1 each way).
My preference wouldn't be to spend too much time in Milan, unless you want to visit
The Last Supper or see the
Duomo. You could substitute the Cinque Terre or Lago di Como for Milan.
I'd suggest 2-3 days in Florence, perhaps two days in Venice (it's expensive!), and at least 4-6 days in Rome (there's LOTS to see - plan your touring carefully).
Salzburg is a beautiful city and it's a good spot to use as a home base for visiting other towns in the region. You could (for example) visit Berchtesgaden or Hallstatt (although spending a few nights in Hallstatt would be a good idea, as it's located in the incredibly beautiful Salzkammergut region - the town is over 5000 years old and has a Salt Mine that can be toured).
I'll leave the sights in Eastern Europe to the rest of the group, as I don't have a lot of information on them.
As usual, I would highly recommend pre-reading the Guidebook
Europe Through The Back Door while you're planning your trip (your friend in Canada will be probably be able to find it in local bookstores - the 2011 edition will be released in the fall, but I don't have the exact date yet). Use country-specific Guidebooks for planning your touring, accommodations and transportation. If you're planning to stay in Hostels, check
www.hihostels.com/dba/continent-EU.en.htm for information.
If you're planning to use a Railpass, note that these DO NOT include fees such as reservations which are compulsory on some trains, nor Couchette fees if you plan on using those.
Good luck with your planning!