It is advisable to give notice before you quit a job, if only because you might need their references later but if you break a contract, nothing can really be done to you. Are there any stipulations in the contract to what happens if you break it?
I knew some guys who had a 2 year contract with the employer and broke it and quit, some completely without notice. The company tried to bill them for their costs of hiring them, actually that was in their contract that they would be billed for that if they broke it but after they talked to the Alberta employment standards, they found out that it was against the law to make them pay these costs and so they told the company that and refused to pay. The company could not do anything to them.
For more help with this, check http://www.cic.gc.ca/english/information/faq/work/caregiver-faq02.asp and http://www.cic.gc.ca/english/information/faq/work/caregiver-faq03.asp