What tax required to be paid? Do we need to pay sales tax during registration? Or some other tax?Yes, you can do that later. Tell the officers that the vehicle is not going to stay in Canada. And if you want to complete the process during your first landing then also its fine....you can still travel to US with that vehicle....There is really no need to worry....
But why you guys want to get your cars here and pay the taxes again which you have already paid in US....and your car's worth might be a little lesser than the similar Canadian car as it is a US car (just my thought)....it might hurt when you'll sell it here...so sell your car there and get a new one here....check the prices on autotrader.ca to get an idea about the price....You may end up paying a little more than US (or may be not) but that'll save you some hassle....
I'm planning to buy new car this year (needed), but have plans to move to Canada only on 2019 or later. I live in a US state that has no sales tax.