Hi there!
I'd highly recommend looking into CAA, my Ontario geography is REALLY poor so here are all of the phone numbers I could pull up for the Ontario CAA's.
CAA NORTH & EAST ONTARIO
2525 Carling Avenue
Ottawa , Ontario K2B 7Z2
www.caaneo.on.ca
(613) 820-1890
1-800-267-8713
CAA SOUTH CENTRAL ONTARIO
60 Commerce Valley Drive East
Thornhill, Ontario L3T 7P9
www.caasco.com
(905) 525-1210
1-800-268-3750
CAA NIAGARA
3271 Schmon Pky
Thorold, ON L2V 4Y6
www.caa.niagara.net
(905) 984-8585
I also HIGHLY recommend Kingdom Magic Vacations (Google them!), this is who we have our current May 2007 vacation booked through. If you go this route ask for Kim; she's wonderful!
The CAA/
AAA vacation rates are typically good except that they only have a select number of rooms so you may be limited on where you can stay. You will also need to purchase a membership through them. Here in Alberta the membership will run you betwen $70 and $80.
The best thing to do is go onto the Disney site and mock plan your vacation to see what Disney will quote you and then get the exact same quote from AAA and/or Kingdom Magic to see how they compare.
With respect to flights, I'm really not that well versed with flying out of Ontario but from what I've seen here on the boards your best bet is to fly out of Buffalo; they seem to get good prices!
If you have any other questions please feel free to ask! We leave in 10 days and will be there for 2 weeks and I've been planning this trip for a while now and I'm pretty well versed in planning.
-Brandt