Just a few points from my experiences.
If you use a
travel agent, make sure they know their product. I have experienced a few (and work in one) that pushes Air Canada Vacations, Westjet Vacations or Sunwing Vacations over any other way of booking Disney and often this is not the best or most flexible deal. There is usually a 100 dollar plus premium on this packages per person and don't include tickets. Tickets are an extra. It is often cheaper, or the same price to book everything separately. Also booking through Disney directly can be much more adventurous because they allow you to apply new discounts to trips while the vacation package companies do not. The only time I recommend a client use one of the vacation companies is if their heart is set on a particular resort that is unavailable through other channels.
As for airports. Price shop. Look at Hamilton, London, Kitchener, Detroit, Buffalo and Toronto. You will be surprised by the price differences between the airports. Don't believe the hype that Detroit or Buffalo are always the better deal. When I am going in May the price difference was only 45 dollars. That extra 45 dollars to fly out of Toronto meant direct flights and not having to cross the border at Niagara/Buffalo which can be less then ideal. Dealing with customs in Pearson is always preferable in my opinion. But I just booked clients on a vacation with flights out of Kitchener because it was a good combination of convenience and price.