You're looking at L-1A I think or E-1 (or possibly E-2, depends on whether this is a completely separate division or whether it is part of the supply chain for the Canadian business). Or possibly both, one after the other.
L-1A (intracompany management transfer) is relatively straightforward to get, you get the paperwork proving that you are setting up an office, will be responsible for managing it, etc. (have a look on the USCIS website for the exact standards to get it) and you can apply at the POE, costs $820. They do check over L-1A applications a bit more closely when you're starting a new office, provided it's a genuine application it's not too hard though.
Dependents get L-2, but only spouses can work on L-2, kids can go to school on L-2. Simply show proof of family ties, such as birth certificates.
In this situation L-1A is valid for one year while you set up the office and can be renewed for two-year periods for a total of seven years, this is the snag with it and why E-1 is a better if you're going to be doing this long-term.
E-1 (treaty trader) is however much harder to get and requires a lot of paperwork. I strongly advise you to use an immigration consultant for E-1 who is familiar with how to apply for them, it requires financial statements and so on for the business. The advantage is that it can be renewed forever in 2-year increments, provided the business keeps going.
The downside to L and E (and nearly all non-immigrant categories) is that your kids have basically no status in the US.
They can go to school but they can't work, and when they turn 21 they have no status at all. They can go to college in F-1 status (which allows limited employment as well) but you would have to pay foreign tuition rates and they can't get student loans.
There's no easy way of going from L-1A or E-1 to permanent resident status either, especially in this situation (because you are the guy in charge). You would only be able to adjust status through some other means, for example if you got married to a US citizen.
Have a poke through this:
http://toronto.usconsulate.gov/content/ ... ment=evisa
Steve.