State University tuition rules vary from state to state. But, broadly speaking all State-Universities have two kinds of tuitions: In-state and out of state.
In-state tuition fees are highly subsidized and are paid by students who are classified as residents of a state.
Out-of-state tuition fees are a few times higher than in-state tuition fees. They supposedly reflect the true cost of education and are not subsidized. International students along with other students who cannot be classified as residents of a given state, pay out-of-state tuition fees.
Since you are moving from Canada, I am assuming that you will be working and paying taxes in your state of residence. In most states you can be classified as a resident if you live there are pay taxes for at least 12 months. There are other requirements like having your cars registered in that state, have a drivers license from that state, have a bank account in that state etc.
If your children are under 18 (under 21 in some states) and depend on you and you fulfill the criteria mentioned in the previous paragraph, they can qualify to pay in-state tuition fees until they claim their own residency in a given state.
The best thing to do would be to Google "CA in-state tuition," (Assuming you were moving to California, or any other state for that matter) and click on any link that has '.edu' in it. It will take you to a page for a University located in that state and give you more information about in-state tuition in the state in which the University is located.
I hope this answers your question.
