Your husband is canadian cit or canadian PR? If so get the PR app in, if the app is in and you are from a visa exempt country shouldnt be a problem. If you're not from visa expemt country best chances of getting extension approved is to file inland application for PR. Then on your visitor extension all i ever said for reason to extend was simply "To live with my wife and children whilst we await out come of inland fmaily sponsorship application" Alot depends on your circumstances, maybe give us a bit more info and one of us can give you a more conculsive answer. There's never any set amount of proof, some officers are fine with the statement, some can ask for proof you will leave. It heavily depends on where you are from. Its rare people from visa expempt countries have any great problems getting an extension unless there's something to make them flag the application.