Two other items we added in when we factored the cost between driving (in the west not the east though) was the cost of the extra vacation time we would need to take and the cost of wear and tear on us, not just our vehicle.
Door to door flying from Calgary to
Disneyland is 7 hours, including going to/from airport, flying time, waiting for plane/luggage/rental car etc, allowing for ample time but of course delays could affect this.
Door to door driving, including an overnight stay, would be close to 40 - factoring in stops, staying overnight on the way, even driving some pretty solid blocks of time. Now granted you are looking at a few hours less from Toronto to Orlando but still it's an extra day pretty much.
If both parents work, that is 4 vacation days, which is not a real out of pocket cost I admit but added to it is that you arrive there and return home exhausted (at least we would) and that really would take away from our vacation experience.
I agree with a PP - if you make the driving part of your trip and you stop and enjoy the journey - then that is a value being added to it. There is also the added value of being able to bring whatever you want with you instead of having to limit your packing. So I think if you embrace it then it can be worth it.
We do not have a Buffalo equivalent here south of Calgary, you'd have to connect from any airport just south of the border to get to Disneyland, and that is another hassle so we watch seat sales and got $1600 for 4 direct from Westjet - not cheap but not crazy expensive either.
Good luck in your planning - it is half the fun sometimes!